"To" and "too," "affect" and "effect," ...

These are errors which occur because two words sound similar or the same, but are spelled differently and have different meanings. Some of the more common soundalike errors:

"Compliment" and "complement"

A "compliment" is a pleasantry, an expression of goodwill, admiration, or respect; "he complimented my typing skills." As a verb, it means "to pay someone a compliment." On the other hand, "complement" means "a complete set," or "to complete or to fit well together with," as in "I have the normal complement of fingers and toes" or "Bob and Jill complement one another beautifully as business partners."

"Allude" and "elude"

To "allude" to something means to refer to it, usually indirectly; "far be it from me to allude to my esteemed rival's history of wombat abuse." "Elude," though, means to escape or avoid; "the suspect eluded police capture by slipping out the window."

"To" and "too"

"Too" means "also" or "to a great extent." "To" means "in the direction of" or indicates an infinitive. You go to the store; if someone else goes along with you, then she goes too. If fifteen people go with you, that's far too many to take one car.

"Accept" and "except"

To "accept" something means to receive that thing; you accept a reward, you accept blame, you accept a FedEx package. "Except" means "with the exclusion of" or "but;" for instance, "I work every day except Saturday and Sunday." Just think: E is for Except, E is for Exclusion.

"Affect" and "effect"

These two words are entirely different parts of speech. "Affect" is a verb: "Your insults do not affect me." "Effect" is generally a noun; that is, it is an actual thing. Slings and arrows have an effect on me; they injure me, and the injuries are things. "You cannot affect me; your idle chatter has no effect on me."

Confusing this issue somewhat is that the word "affect," when the emphasis is placed on the first syllable, is used in the psychiatric community to mean "emotion" or "demeanor," as in "Bob presents a flat affect when you talk to him" (that is, Bob shows no emotion or expression when you're speaking to him); and the word "effect" can be used as a verb to mean "make" or "change," as in "to effect an improvement in the situation."

"Allowed" and "aloud"

"Allowed" means "permitted," as in "I am not allowed to go to the party tomorrow." "Aloud" means "out loud," as in "Read the book aloud." The word "aloud" has the word "loud" in it, which makes these two easy to remember.

"Advise" and "advice"

These two words are also different parts of speech. "Advise" is a verb; you advise someone to do something. "As your lawyer, I advise you to keep your mouth shut." It's pronounced "advize." "Advice" is something that you give someone, or someone gives you. "I did not follow my lawyer's advice, and now I'm in trouble."

"Desert" and "dessert" and "deserts"

This is a very common confusion, even among people who really ought to know better. A "desert" is a place with no water; "We are reading a book about the Sahara Desert." As a verb, "desert" means "to abandon," as in "I may have to desert my Hummer if gas keeps getting more expensive." On the other hand, "dessert" is the treat you have after a meal, as in "Can I have apple pie for dessert tonight?"

This one gets really confusing when you see or hear the phrase "just deserts." Many people erroneously believe that this should be "just desserts;" however, the word "deserts" in this case is an archaic expression meaning "that which someone deserves." A person's "deserts" once meant "the thing a person deserves to have;" thus, "just deserts" means "those things it is just for one to have."

"Discreet" and "discrete"

These words sound the same, but are completely unrelated. "Discreet" means "unobtrusive" or "with good judgement," as in "If you are going to follow someone, it's best to be discreet." A person who is discreet shows discretion, as in "Discretion is the better part of valor." "Discrete," on the other hand, means "made up of distinct parts," as in "A telephone has three discrete parts: a handset, a base, and a cord."

"Lose" and "loose"

"Lose" is pronounced "looze." It means "to misplace," as in "I always lose my car keys," or "to be defeated," as in "We will lose the game without Bob." "Loose" means "not tight" ("This shirt is too loose on me"), or "not confined" ("the dog got loose when the door on his kennel broke").

"Site" and "sight" and "cite"

"Site" is a place. "Sight" is having to do with vision. "We went to the crash site" means "we went to the place where the crash happened;" "the enemy is in sight" means "the enemy is visible." This is a web site, meaning "a place on the Web," not a web sight. "Cite," which is pronounced just like "site," is entirely different; it means to quote, as in "Can you cite any studies that prove what you're saying?"

"Then" and "than"

"Then" has to do with time, as in "We went to the store, then we went to the movies" or "When you finish your homework, then you can go outside." On the other hand, "than" is a conjunction used in comparisons: "He is older than she is," or "that is easier said than done."

"Brakes" and "breaks"

"Brakes" are devices used to stop a moving machine, such as a car. "Breaks" is what happens when something hits something else too hard. If the brakes on your car fail, your car breaks when it hits the wall; a broken brake leads to a broken car.

It's "per se," not "per say."

Per se is Latin for "of itself." It means "intrinsically," as in "a state government is not a sovereign entity per se, but is subsumed under the Federal government."

"Imput," "forte" ...

The word "vice" in "vice versa" is not pronounced "vis-uh."

"Vice versa" is Latin for "order reversed;" for example, "I sometimes chase my cat around the room, and vice versa" means "I sometimes chase my cat around the room, and the cat sometimes chases me." People sometimes pronounce the "vice" as though it were a two-syllable word rhyming with "versa," as in "vis-uh vers-uh," which is incorrect, at least in modern pronounciation. (It's been recently pointed out to me that the original Latin would probably have been pronounced 'Wi-ke Wer-sa' or 'Vi-che Ver-sa,' rather than as it's typically pronounced today 'Vise Ver-sa'--though in no case is 'Vis-uh' correct.)

It's "input," not "imput."

"Input" is what you feed into a system--you offer someone your input, you feed input into a computer program. It literally comes from "something you put in." More and more often, people are spelling it "imput," particularly online; this points, I think, to an error in pronunciation.

The word forte is most properly pronounced "fort," not "for-TE" or "for-TAY"

"Forte" derives from the French "fort," meaning "strong." A person's "forte" is his strongest talent, as in "running a business is Bill's forte." It's often pronounced as two syllables, "for-TAY," in the United States, though this is not technically correct; that pronunciation would be more correct if the word had derived from Italian, not French.

Note: Apparently, there is some debate about the proper pronunciation of this word. My references list "fort" as the correct pronunciation, but the Merriam-Webster online reference has this to say:

we have a word derived from French that in its "strong point" sense has no entirely satisfactory pronunciation. Usage writers have denigrated \'for-"tA\ and \'for-tE\ because they reflect the influence of the Italian-derived "forte." Their recommended pronunciation \'fort\, however, does not exactly reflect French either: the French would write the word "le fort" and would rhyme it with English "for." So you can take your choice, knowing that someone somewhere will dislike whichever variant you choose.

It's "espresso," not "expresso."

There is no hard "K" sound in the name of the popular coffee beverage, legions of Starbucks cashiers to the contrary.

"Its" and "it's," "you're" and "your," ...

"You're" vs "your," "they're" vs "there" and "their"

If a pronoun has an apostrophe in it, it's a contraction. "You're" means "you are," always. "Your" means "belonging to you."

The same is true of "they're" and "their." "They're" has an apostrophe; it is a contraction. It means "they are." "Their" means "belonging to them." "There" means "somewhere that is not here."

"Its" and "it's"

This is probably the single most common grammar mistake on earth. People get confused about this one because they remember a rule from their childhood days: possessive nouns get an apostrophe. "That is Bob's car." "That is the horse's barn."

Problem is, the word "it" is not a noun. It's a pronoun! Pronouns never, ever, ever get an apostrophe to indicate possession. Think about it: You don't say "mi'ne" or "hi's" or "her's"--and you don't say "your's" or "it's" to indicate possession.

"It's" means "it is" or "it has." If you get confused, take out "it's" and put in "it is." If the sentence makes no sense, don't use the apostrophe.

"A group of people is going to the movies," "a bunch of marbles is on the floor" ...

The subject of a sentence and the verb of a sentence must agree with one another: "A person is smart, people are dumb, stupid panicky animals." This can get a little complicated, though, when there are prepositional phrases between the subject and the verb: "A bunch of people spells trouble."

The subject of a sentence is never found in a prepositional phrase; if a noun appears after a word like of, the one thing you can be sure of is that it's not the subject. Collective nouns such as "group" and "bunch" and "pile" are singular, not plural; the plural versions are groups, bunches, and piles. So you would say "A group is going" or "Two groups are going."

When a prepositional phrase follows the subject, the verb must still agree with the subject, not the prepositional phrase. So you would say "A group of people is going to the movies," not "a group of people are going to the movies"--the phrase 'of people' is a prepositional phrase, and is not the subject of the sentence.

On a similar note, the proper first-person pronouns used as objects of prepositions and active verbs are "me" and "us," not "I" and "we." For example, "can you give Tommy and me a ride to the store" is correct; "can you give Tommy and I a ride to the store" is not. When you remove Tommy from the equation, this becomes easier to see; you would say "Can you give me a ride" but never "Can you give I a ride" or "Can you give myself a ride."

"Orientate," "preventative," ...

These are errors which occur when someone attempts to add prefixes or suffixes to a word inappropriately, resulting in an awkward or incorrect construction.

It's "administer," not "administrate."

When you supervise something, or when you apply something or dispense something, you are "administering" that thing, not "administrating" that thing. You would correctly say "Bob will administer bandages and aspirin," not "Bob will administrate bandages and aspirin." (Some references are beginning to recognize "administrate" as an acceptable, but less preferred, alternative.)

It's "preventive," not "preventative."

Something which is designed to prevent something else from happening is a preventive measure, as in "aspirin can act as preventive medicine for heart attacks."

It's "orient," not "orientate."

When you have your bearings, you are properly "oriented." The process of becoming oriented is called "orientation," but if you are giving something or someone its bearings, you are orienting it, not orientating it.

It's "regardless," not "irregardless."

This one is a bit confusing, because "irrespective" is the correct form of "not respective" (as in "all employees receive the same vacation benefits irrespective of their seniority"), but the correct form of "without regard to" is "regardless," not "irregardless."

It's "empathic," not "empathetic."

"Empathy" is the ability to understand and identify with another person's feelings. A person who has a high degree of empathy is a person who is good at understanding the feelings of other people, and is said to be "empathic."

"I couldn't care less," "nothing fazes me," ...

These are errors which occur because two words may be confused, or because someone has misstated a common expression and hasn't really thought about it. Some of these may involve soundalike errors as well. For example:

"Exacerbate" and "exasperate."

These two words are pronounced differently, but often confused in writing. "Exacerbate" is pronounced like "eg-ZA-ser-bate" and means "to make worse," as in "skydiving may exacerbate a torn ligament" or "shooting people may exacerbate hostilities." On the other hand, "exasperate," which is pronounced "eg-ZAS-peh-rate," means "to irritate or annoy," as in "sitting in traffic really exasperates me."

It's "bated breath," not "baited breath."

The word "bated" is archaic, and almost never used any more. It's a derivation of "abated," which meaned "lessened."

To have "bated breath" means to be holding one's breath (literally, one's breathing has been abated), because of some emotion such as fear or anticipation. "I had bated breath" is the equivalent of saying "I held my breath." "I had baited breath," on the other hand, means "my breath smells like bait," which is kind of nasty.

"Dominant" and "dominate."

These two words are often confused, but they're entirely different parts of speech. "Dominant" is an adjective ("The pack is led by the dominant male") or, in the BDSM subculture, a noun (a "dominant" is a person who assumes the controlling role in erotic power exchange). "Dominate" is a verb that means to exert control over; "The dominant male in the wolf pack dominates the other wolves."

When speaking of agreement, it's "jibe," not "jive."

To "jibe" means to agree, as in His account of the crime did not jibe with the other eyewitness accounts. "Jive" is a style of dance.

"Literally" means "actually."

Something is literally true if it is actually true; "literally" is the opposite of "metaphorically" or "figuratively." So if you say "I am so happy I am literally walking on air," what you mean is you are so happy that your body is now violating the law of gravity and your feet are no longer in contact with the ground.

Many people say "literally" when they mean "figuratively." If you are hungry, but you are not in the hospital being treated for malnourishment, you are not "literally starving."

One thing can not be "more unique" than another, or "very unique."

"Unique" means "one of a kind." It's based on the Latin "unus," meaning "one." Something can not be "very one-of-a-kind" or "more one-of-a-kind" than another; the word "unique" should not be used with modifiers.

Something that is not directly relevant is "beside the point," not "besides the point."

When a particular part of a conversation or argument is not directly relevant to the main point of that conversation or argument, but is tangentially related, it is said to be "beside the point"--that is, not directly on point. "Besides the point" is incorrect usage; "besides" means "except" or "in addition to," so it seems likely that this confusion may have arisen from the idea that the expression means "that is in addition to the point," which is not correct.

"Bald-faced liar" and "bold-faced liar" are both correct, but mean different things.

I'm often asked which is the correct expression, "He was a bald-faced liar" or "She was a bold-faced liar." Both expressions are correct; "bald-faced liar" is a modern expression, and "bold-faced liar" dates back to the 1500s.

A "bald-faced liar" is a person who tells simple, obvious lies. "Bald" in this context means "unadorned" or "obvious," rather than "hairless." A "bold-faced liar" is a person who lies in a strong, confident, self-certain way; the expression "bold-faced" literally means "in a bold manner."

There is a third variant as well, which is not often used: "bare-faced liar." It means something slightly different as well; according to Merriam-Webster, "bare-faced" is an idiom meaning "without scruples." A "bare-faced liar" is an unethical or unscrupulous liar.

"Disinterested" and "uninterested" do not mean the same thing!

The word "disinterested" means "impartial." A judge in a courtroom should be disinterested in the outcome; that is, the judge should not have any vested interest one way or the other, and he should be impartial to the issue being determined.

"Uninterested" means "not interested in;" for example, "Bob is uninterested in football" means Bob does not care about football. A courtroom judge is (or should be) disinterested, but he is not uninterested!

"Disorganized" and "unorganized" do not mean the same thing!

The word "unorganized" simply means "not organized." A cluttered desk may be unorganized, yet the person who works at it might still be able to find everything on it. "Disorganized" means "not organized" with connotations of dysfunction; it's used to describe something that is not only unorganized, but unorganized in a way that makes work difficult or makes finding things impossible.

"Altogether" and "all together" do not mean the same thing!

"All together" means "all in one group," as in "let's keep the socks all together." On the other hand, "altogether" means "completely," as in "His speech was altogether full of hot air."

"Farther" and "further" do not mean the same thing!

"Farther" is used when you are talking about distance: "San Francisco is farther from Tampa than Atlanta is." "Further" is used when you're speaking of abstract ideas or talking metaphorically; "San Francisco goes further to deal with urban sprawl than Atlanta does."

"Less" and "fewer" do not mean the same thing!

"Less" is used in situations where you're talking about something that's not discrete or easily quantified: "This car uses less gas than my old car." "Fewer," on the other hand, is used in situations where you are talking about a countable quantity of discrete objects: "The express lane is only for people with eight items or fewer," "fewer people voted for John than for Jake." The signs you see in supermarkets reading "Express Lane: Eight items or less?" Wrong.

It's "for all intents and purposes," not "for all intensive purposes."

"For all intents and purposes" means "for all practical purposes." Many people erroneously write "for all intensive purposes," which would, presumably, mean for purposes that are not casual, or perhaps for purposes that are trivial--near to the opposite of the phrase's intent.

When the details of a plan or idea are filled in, the plan or idea has been "fleshed out," not "flushed out."

One talks metaphorically of taking an idea that is sketchy--in other words, the skeleton of an idea--and "fleshing it out," or completing it. I'm not quite sure how one would "flush out" an idea, but the process doesn't sound very sanitary...

It's "embedded," not "imbedded."

"Embedded" means "set within" or "enclosed." If you put a bottle cap in wet cement, when it hardens, the bottle cap becomes embedded in the cement. An embedded computer is a computer set in something else, like a microwave oven or a cell phone.

It's "pronunciation," not "pronounciation."

A reader of this site pointed out to me that this is an error I'd made myself--right here on this very page! "Pronounciation" is not actually a word at all; the way a word is pronounced is its "pronunciation."

Interestingly, a Google search for "pronounciation," which is the error, turns up over a million hits, whereas a search for the correct "pronunciation" turns up about 41 million hits, which suggests that at least one in 41 people makes this mistake.

It's "shudder to think," not "shutter to think."

To "shudder" is to tremble, as from fright; "shudder to think" means "the thought of that is so frightening (or disturbing or whatever) that the very thought of it is enough to make me shudder."

It's "bear with me," not "bare with me."

To "bear" something means to carry it, as in "to bear arms," or to toil with as a burden; "I can't bear this heavy backpack," or, more figuratively, "I can't bear this pain." "Bear with me" means "carry along with me;" "bare with me" means "get naked with me."

It's "should have," not "should of."

"Have" is a verb; "of" is a preposition. "I should have gone" or "I would have gone if I had the money" are correct. "I should of gone" or "I would of gone" are incorrect; the word "gone" is not part of a prepositional phrase.

Something you make is your "handiwork," not your "handywork."

The word "handiwork" comes from the Middle English handiwerk, which in turn derives from the Old English hand gework, literally, "the work produced by the hands." It's the result of your skill or labor: "this model train set is my handiwork." A person skilled with his hands, especially at odd jobs, is said to be "handy," and a person who does a number of odd jobs is sometimes called a "handyman," which is probably how the confusion regarding "handiwork" and "handywork" got started. A handyman produces handiwork, not handywork.

It's "death knell," not "death nail."

The word "knell" is an archaic term meaning "to sound in an ominous manner, as the ringing of a bell to indicate a death or disaster." A "death knell" is literally the sound of a funeral bell.

It's "A lot," never "alot."

"A lot" is two words, as in "We have a lot of food in the kitchen" or "Florida is being hammered by a lot of hurricanes this season." It means "A large quantity." You would never say "abunch;" it's two words--"a bunch." Same thing. And "allot" means something else entirely; "allot" is a verb, meaning "to assign" or "to distribute," as in "Bob will allot one donut and one cup of coffee to each attendee."

It's a "moot point," not a "mute point."

Something is "moot" if it is debatable or of undecided value; if you don't live in Florida, then the fact that Florida residents get discounted Disney World tickets is moot to you. "Mute" means "unable to make a sound."

It's "hear hear," not "here here."

"Hear hear" means something like the more contemporary vernacular "I hear you;" it indicates agreement and assent. "Here here" means "not over there there," and that's just kind of silly.

It's "Lo and behold," not "low and behold."

The word "lo!" is a Middle English expression of surprise. "Lo and behold" is kind of the equivalent of saying "Well, hey, look at that!"

It's "Nothing fazes me," not "nothing phases me."

To "faze" is to disturb or frighten. "She was unfazed" means "she retained her composure." "He was unphased" means "he was not made of a number of waveforms that were in synchronization." Big difference, folks.

"I couldn't care less," not "I could care less."

"I could care less" means "I do care." It would be possible for me to care less, because I already care. If I do not care at all--if the amount I care about something is zero--then it would be impossible for me to care any less, because I can't care about something less than a zero amount...I couldn't care less.

It's "etc," not "ect."

"Etc" is an abbreviation for "et cetera" (two words), which is Latin for "and so forth." "Et" means "and," which is why "etc" is sometimes written "&c". "Etc" is correct. "&c" is correct but archaic. "Ect" is not, never has been, and never will be correct.

The abbreviations "ie" and "eg" do not mean the same thing!

You use "ie" when you mean "in other words" or "that is to say." It's Latin for "id est," which means "that is." For example: "He is a businessman; ie, he makes his money by operating a business." On the other hand, "eg" is used to mean "for example." It's Latin for "exempli gratia." "I do not like spectator sports--eg, football and baseball." Most properly, they are written "i.e." and "e.g.," though "ie" and "eg" are becoming more common.

For example: eg. In other words: ie.

"Insure" and "ensure" do not mean the same thing either!

"Ensure" means "to make sure of." Double-check your math on your tax return to ensure you don't get an embarrassing phone call from the IRS. "Insure," on the other hand, means "to provide insurance for," you insure your house in order to ensure that you won't be financially ruined if it burns down.

To be caught "between the devil and the deep blue sea" does not mean "between two unattractive options."

It means "to be in a position where you have no room to maneuver." There are two theories about the origin of this expression. The first is the idea that the 'devil' on a wooden sailing ship was a term for the main spar of the ship--a brace that runs the whole length of the ship from front to back, around which the frame of the ship is built. There is a very narrow space--typically less than 3' high--between a ship's devil and the bottom of the hull; this was sometimes the space where the most lowly members of a ship's crew slept, quite literally "between the devil and the deep blue sea." It's a very, very tiny space. The other is that the seams on a wooden ship near the waterline were often referred to as the "devil," and that sealing these seams to keep them watertight involved a sailor being lowered over the side of the ship on a rope, with a bucket of sealing pitch; such a sailor was dangling precariously "between the devil and the deep blue sea." (I've seen one Web page which claims that the expression predates the days of wooden sailing ships, but I haven't seen any documented usage of the term that dates back that far.)

"You have piqued my interest," not "you have peaked my interest" or "you have peeked my interest."

The word "pique" (pronounced like "peek") means "to excite or arouse." "You have piqued my interest" means "you have aroused my interest"--that is, I wasn't interested before, but now I am.

A group is a "clique," not a "click"

"Clique" is pronounced like "click." However, the meaning is completely different. "Clique" was originally a French word; hence the weird spelling.

Something that's stylish is "chic," not "sheik"

"Chic" is another confusing French import. It's pronounced like "sheik" but means "elegant, stylish, or sophisticated."

It's "whet my appetite," not "wet my appetite."

"Whet" means "sharpen." A tool that sharpens a knife is called a "whetstone." To "whet" one's appetite means to sharpen one's appetite--"That appetizer really whetted my appetite!" To "wet" one's appetite means to make it soggy.

Usage that's changing

No language ever stands still. The English language is a dynamic, living thing, and that means rules of grammar can and do change over time. Words become archaic; rules of grammar change; even spelling and usage change over time.

There are many areas where English is in transition right now. A few of them are outlined below.

"Nauseated" and "nauseous."

Originally, "nauseated" meant "sick to your stomach;" if the smell of tuna fish turns your stomach, you can say that tuna makes you nauseated. "Nauseous" meant "causing nausea in others." If you are "nauseous," that means you make other people sick. However, these two terms are used interchangeably so often that some references are now beginning to list "nauseated" as a synonym for "nauseous."

"All right" is generally more acceptable than "alright."

"All right" means "okay." Literally, "all is right." It's not one word. This rule is beginning to bend, though; the newest Oxford English Dictionary lists "alright." I get a lot of email, pro and con, on the acceptability of "alright," which is further confused by the fact that some dictionaries and books on English usage still condemn it, while others have begun to accept it.

"Judgment" is generally more acceptable than "judgement."

Traditionally, one who judges another is said to pass judgment. Increasingly, more and more reference texts are listing "judgement" as an acceptable variant to "judgment," though not everyone finds "judgement" acceptable.

I personally prefer "judgement," as I think it's more logically consistent. Other words ending in the letter "e" keep that "e" when adding a -ment suffix (as in "atonement," for example); and the word derives most immediately from the Middle English jugement, so keeping the "e" seems reasonable to me.

"Sneaked," not "snuck," is generally the preferred past tense of "sneak."

In formal or professional writing, it's generally considered more proper to say "the burglar sneaked into the room" than "the burglar snuck into the room." However, this rule is also beginning to bend; my dictionary considers "snuck" an acceptable, but less preferred, past tense form of "sneak."

To me, "snuck" sounds clumsy. While I'll grudgingly accede to the fact that it's a very common usage, that doesn't mean I have to like it!

"Interface" is properly a noun, not a verb.

An interface is a place where two different things come together or interact with each other. A physicist might talk about how light diffracts at an air-water interface, meaning the point where the air meets the water; a computer technician might speak of an interface where a printer is connected to a computer; a computer programmer might speak of the interface that a program presents for interaction with a person.

The first time I heard the word "interface" used as a verb (as in "Let's see if we can get this database server to interface with this client"), I cringed. Then I heard the word "interface" used to refer to interactions between people (as in "Let's see if we can have our sales reps interface with the design department on that issue"). Ugh!

This usage is becoming common enough now that some dictionaries have begun listing "interface" as a verb.

Indeed, modern English in popular usage seems to be moving more and more in the direction of blurring the line between nouns and verbs; I saw a bumper sticker a while ago reading "Stop Noun Verbification: Don't Verb Your Nouns."

Commas in lists

In the past, a list of words or phrases separated by commas would include a comma after each word or phrase in the list: "I like apples, peaches, pears, and bananas." Today, it is beincoming increasingly common to omit the comma before the second to last word in the list, and indeed this is the preferred usage according to some style manuals: "I like apples, peaches, pears and bananas."

However, this new usage creates potential ambiguities. As a friend of mine recently pointed out, in a sentence such as "I am an expert at hardware design, software and firmware validation, analysis and reverse engineering of products, and user interfaces," that final comma is essential to making the sentence comprehensible. Under the newer preferred usage, the sentence would read "I am an expert at hardware design, software and firmware validation, analysis and reverse engineering of products and user interfaces." Without the comma, it seems as though "analysis and reverse engineering of products and user interfaces" means "analysis and reverse engineering of products" and "analysis and reverse engineering of user interfaces"--that is, it is not clear that "analysis and reverse engineering" applies only to "products" and does not modify both "products" and "user interfaces."

"Data" and "datum," "phenomena" and "phenomenon," ...

English has a long history of borrowing words from other languages--many of which don't follow standard English rules for pluralization. As a result, there are many English words which are normally plural, but don't look plural because they don't end in the letter S. A partial list: