Using the right word can matter. Using the wrong word can matter even more. I once lost a potential writing gig because I used "who" instead of "whom" in a proposal letter.

(And I still have trouble getting "who" and "whom" right.)

Even just one incorrectly used word--especially when you're trying to make a great impression--can ruin everything. Is that unfair? Yes... but it does happen.

To make sure that doesn't happen to you, I've collected some of the most common incorrectly used words from other posts into one epic post. (Thanks to all the readers along the way who offered their own examples, many of which are included here.)

Here we go.

Adverse and averse

Adverse means harmful or unfavorable: "Adverse market conditions caused the IPO to be poorly subscribed." Averse refers to feelings of dislike or opposition: "I was averse to paying $18 a share for a company that generates no revenue."

But, hey, feel free to have an aversion to adverse conditions.

Advise and advice

Aside from the two words being pronounced differently (the s in advise sounds like a z), advise is a verb while advice is a noun. Advice is what you give (whether or not the recipient is interested in that gift is a different issue altogether) when you advise someone.

So "Thank you for the advise" is incorrect, while "I advise you not to bore me with your advice in the future" is correct if pretentious.

If you run into trouble, just say each word out loud and you'll instantly know which makes sense; there's no way you'd ever say "I advice you to..."

Affect and effect

Verbs first. Affect means to influence: "Impatient investors affected our roll-out date." Effect means to accomplish something: "The board effected a sweeping policy change."

How you use effect or affect can be tricky. For example, a board can affect changes by influencing them and can effect changes by directly implementing them. Bottom line, use effect if you're making it happen, and affect if you're having an impact on something that someone else is trying to make happen.

As for nouns, effect is almost always correct: "Once he was fired he was given 20 minutes to gather his personal effects." Affect refers to an emotional state, so unless you're a psychologist you probably have little reason to use it.

Aggressive and enthusiastic

Aggressive is a very popular business adjective: aggressive sales force, aggressive revenue projections, aggressive product rollout. But unfortunately, aggressive means ready to attack, or pursuing aims forcefully, possibly unduly so.

So do you really want an "aggressive" sales force?

Of course, most people have seen aggressive used that way for so long they don't think of it negatively; to them it just means hard-charging, results-oriented, driven, etc., none of which are bad things.

But some people may not see it that way. So consider using words like enthusiastic, eager, committed, dedicated, or even (although it pains me to say it) passionate.

Award and reward

An award is a prize. Musicians win Grammy Awards. Car companies win J.D. Power awards. Employees win Employee of the Month awards. Think of an award as the result of a contest or competition.

A reward is something given in return for effort, achievement, hard work, merit, etc. A sales commission is a reward. A bonus is a reward. A free trip for landing the highest number of new customers is a reward.

Be happy when your employees win industry or civic awards, and reward them for the hard work and sacrifices they make to help your business grow.

Between and among

Use between when you name separate and individual items. Take "The team will decide between Mary, Marcia, and Steve when we fill the open customer service position." Mary, Marcia, and Steve are separate and distinct, so between is correct.

Use among when there are three or more items but they are not named separately. Like, "The team will decide among a number of candidates when we fill the open customer service position." Who are the candidates? You haven't named them separately, so among is correct.

And we're assuming there are more than two candidates; otherwise you'd say between. If there are two candidates you could say, "I just can't decide between them."

Bring and take

Both have to do with objects you move or carry. The difference is in the point of reference: You bring things here and you take them there. You ask people to bring something to you, and you ask people to take something to someone or somewhere else.

"Can you bring an appetizer to John's party"? Nope.

Compliment and complement

Compliment means to say something nice. Complement means added to, enhanced, improved, completed, or brought close to perfection.

I can compliment your staff and their service, but if you have no current openings you have a full complement of staff. Or your new app may complement your website.

For which I may decide to compliment you.

Continuously and continually

Both words come from the root continue, but they mean very different things. Continuously means never ending. Hopefully your efforts to develop your employees are continuous, because you never want to stop improving their skills and their future.

Continual means whatever you're referring to stops and starts. You might have frequent disagreements with your co-founder, but unless those discussions never end (which is unlikely, even though it might feel otherwise), then those disagreements are continual.

That's why you should focus on continuous improvement but plan to have continual meetings with your accountant: The former should never, ever stop, and the other (mercifully) should.

Criterion and criteria

A criterion is a principle or standard. If you have more than one criterion, those are referred to as criteria.

But if you want to be safe and you only have one issue to consider, just say standard or rule or benchmark. Then use criteria for all the times there are multiple specifications or multiple standards involved.

Discreet and discrete

Discreet means careful, cautious, showing good judgment: "We made discreet inquiries to determine whether the founder was interested in selling her company."

Discrete means individual, separate, or distinct: "We analyzed data from a number of discrete market segments to determine overall pricing levels." And if you get confused, remember: You don't use "discretion" to work through sensitive issues; you exercise discretion.

Elicit and illicit

Elicit means to draw out or coax. Think of elicit as the mildest form of extract. If one lucky survey respondent will win a trip to the Bahamas, the prize is designed to elicit responses.

Illicit means illegal or unlawful, and while I suppose you could elicit a response at gunpoint, you probably shouldn't.

Everyday and every day

Every day means, yep, every day -- each and every day. If you ate a bagel for breakfast each day this week, you had a bagel every day.

Everyday means commonplace or normal. Decide to wear your "everyday shoes" and that means you've chosen to wear the shoes you normally wear. That doesn't mean you have to wear them every single day; it just means wearing them is a common occurrence.

Another example is along and a long: Along means moving in a constant direction or a line, or in the company of others, while a long means of great distance or duration. You wouldn't stand in "along line," but you might stand in a long line for a long time, along with a number of other people.

A couple more examples: a while and awhile, and any way and anyway.

If you're in doubt, read what you write out loud. It's unlikely you'll decide, "Is there anyway (say it fast) you can help me?" sounds right. "Is there any (small pause) way you can help me?" does.

Evoke and invoke

To evoke is to call to mind; an unusual smell might evoke a long-lost memory. To invoke is to call upon something: help, aid, or maybe a higher power.

So hopefully all your branding and messaging efforts evoke specific emotions in potential customers. But if they don't, you might consider invoking the gods of commerce to aid you in your quest for profitability.

Or something like that.

Farther and further

Farther involves a physical distance: "Florida is farther from New York than Tennessee." Further involves a figurative distance: "We can take our business plan no further."

So, as we say in the South (and that "we" has included me), "I don't trust you any farther than I can throw you," or "I ain't gonna trust you no further."

Fewer and less

Use fewer when referring to items you can count, like "fewer hours" or "fewer dollars."

Use "less" when referring to items you can't (or haven't tried to) count, like "less time" or "less money."

Good and well

Anyone who has children uses good more often than he or she should. Since kids pretty quickly learn what good means, "You did good, honey" is much more convenient and meaningful than "You did well, honey."

But that doesn't mean good is the correct word choice.

Good is an adjective that describes something; if you did a good job, then you do good work. Well is an adverb that describes how something was done; you can do your job well.

Where it gets tricky is when you describe, say, your health or emotional state. "I don't feel well" is grammatically correct, even though many people (including me) often say, "I don't feel too good." On the other hand, "I don't feel good about how he treated me" is correct; no one says "I don't feel well about how I'm treated."

Confused? If you're praising an employee and referring to the outcome say, "You did a good job." If you're referring to how the employee performed say, "You did incredibly well."

And while you're at it, stop saying good to your kids and use great instead, because no one -- especially a kid -- ever receives too much praise.

If and whether

If and whether are often interchangeable. If a yes/no condition is involved, then feel free to use either: "I wonder whether Jim will finish the project on time?" or "I wonder if Jim will finish the project on time?" (Whether sounds a little more formal in this case, so consider your audience and how you wish to be perceived.)

It gets trickier when a condition is not involved. "Let me know whether Marcia needs a projector for the meeting" isn't conditional, because you want to be informed either way. "Let me know if Marcia needs a projector for the meeting" is conditional because you want to be told only if she needs one.

And always use if when you introduce a condition. "If you hit your monthly target, I'll increase your bonus," is correct; the condition is hitting the target and the bonus is the result. "Whether you are able to hit your monthly target is totally up to you," does not introduce a condition (unless you want the employee to infer that your thinly veiled threat is a condition of ongoing employment).

Impact and affect (and effect)

Many people (including, until recently, me) use impact when they should use affect. Impact doesn't mean to influence; impact means to strike, collide, or pack firmly.

Affect means to influence: "Impatient investors affected our rollout date."

And to make it more confusing, effect means to accomplish something: "The board effected a sweeping policy change."

How you correctly use effect or affect can be tricky. For example, a board can affect changes by influencing them and can effect changes by directly implementing them. Bottom line, use effect if you're making it happen, and affect if you're having an impact on something that someone else is trying to make happen.

As for nouns, effect is almost always correct: "Employee morale has had a negative effect on productivity." Affect refers to an emotional state, so unless you're a psychologist, you probably have little reason to use it.

So stop saying you'll "impact sales" or "impact the bottom line." Use affect.

(And feel free to remind me when I screw that up, because I feel sure I'll backslide.)

Imply and infer

The speaker or writer implies, which means to suggest. The listener or reader infers, which means to deduce, whether correctly or not.

So I might imply you're going to receive a raise. And you might infer that a pay increase is imminent. (But not eminent, unless the raise will somehow be prominent and distinguished.)

Insure and ensure

This one's easy. Insure refers to insurance. Ensure means to make sure.

So if you promise an order will ship on time, ensure that it actually happens. Unless, of course, you plan to arrange for compensation if the package is damaged or lost -- then feel free to insure away.

(While there are exceptions where insure is used, the safe move is to use ensure when you will do everything possible to make sure something happens.)

Irregardless and regardless

Irregardless appears in some dictionaries because it's widely used to mean "without regard to" or "without respect to," which is also what regardless means.

In theory the ir-, which typically means "not," joined up with regardless, which means "without regard to," makes irregardless mean "not without regard to," or more simply, "with regard to."

Which probably makes it a word that does not mean what you think it means.

So save yourself a syllable and just say regardless.

Mute and moot

Think of mute like the button on your remote; it means unspoken or unable to speak. In the U.S., moot refers to something that is of no practical importance; a moot point is one that could be hypothetical or even (gasp!) academic. In British English, moot can also mean debatable or open to debate.

So if you were planning an IPO, but your sales have plummeted, the idea of going public could be moot. And if you decide not to talk about it anymore, you will have gone mute on the subject.

Number and amount

I goof these up all the time. Use number when you can count what you refer to: "The number of subscribers who opted out increased last month." Amount refers to a quantity of something that can't be counted: "The amount of alcohol consumed at our last company picnic was staggering."

Of course it can still be confusing: "I can't believe the number of beers I drank" is correct, but so is, "I can't believe the amount of beer I drank." The difference is you can count beers, but beer, especially if you were way too drunk to keep track, is an uncountable total and makes amount the correct usage.

Peak and peek

A peak is the highest point; climbers try to reach the peak of Mount Everest. Peek means quick glance, as in giving major customers a sneak peek at a new product before it's officially unveiled, which hopefully helps sales peak at an unimaginable height.

Occasionally a marketer will try to "peak your interest" or "peek your interest," but in that case the right word is pique, which means "to excite." (Pique can also mean "to upset," but hopefully that's not what marketers intend.)

Precede and proceed

Precede means to come before. Proceed means to begin or continue. Where it gets confusing is when an -ing comes into play. "The proceeding announcement was brought to you by..." sounds fine, but preceding is correct since the announcement came before.

If it helps, think precedence: Anything that takes precedence is more important and therefore comes first.

Principle and principal

A principle is a fundamental: "Our culture is based on a set of shared principles." Principal means primary or of first importance: "Our startup's principal is located in NYC." (Sometimes you'll also see the plural, principals, used to refer to executives or relatively co-equals at the top of a particular food chain.)

Principal can also refer to the most important item in a particular set: "Our principal account makes up 60 percent of our gross revenues."

Principal can also refer to money, normally a sum that was borrowed, but can be extended to refer to the amount you owe -- hence principal and interest.

If you're referring to laws, rules, guidelines, ethics, etc., use principle. If you're referring to the CEO or the president (or an individual in charge of a high school), use principal.

Slander and libel

Don't like what people say about you? Like slander, libel refers to making a false statement that is harmful to a person's reputation.

The difference lies in how that statement is expressed. Slanderous remarks are spoken while libelous remarks are written and published (which means defamatory tweets could be considered libelous, not slanderous).

Keep in mind what makes a statement libelous or slanderous is its inaccuracy, not its harshness. No matter how nasty a tweet, as long as it's factually correct it cannot be libelous. Truth is an absolute defense to defamation; you might wish a customer hadn't said something derogatory about your business, but if what that customer said is true, then you have no legal recourse.

Stationary and stationery

You write on stationery. You get business stationery, such as letterhead and envelopes, printed.

But that box of envelopes is not stationary unless it's not moving -- and even then it's still stationery.

Sympathy and empathy

Sympathy is acknowledging another person's feelings. "I am sorry for your loss" means you understand the other person is grieving and want to recognize that fact.

Empathy is having the ability to put yourself in the other person's shoes and relate to how the person feels, at least in part because you've experienced those feelings yourself.

The difference is huge. Sympathy is passive; empathy is active. (Here's a short video by Bren Brown that does a great job of describing the difference, and explains how empathy fuels connection while sympathy drives disconnection.)

Know the difference between sympathy and empathy, live the difference, and you'll make a bigger difference in other people's lives.

Systemic and systematic

If you're in doubt, systematic is almost always the right word to use. Systematic means arranged or carried out according to a plan, method, or system. That's why you can take a systematic approach to continuous improvement, or do a systematic evaluation of customer revenue or a systematic assessment of market conditions.

Systemic means belonging to or affecting the system as a whole. Poor morale could be systemic to your organization. Or bias against employee diversity could be systemic.

So if your organization is facing a pervasive problem, take a systematic approach to dealing with it -- that's probably the only way you'll overcome it.

Then and than

Then refers in some way to time. "Let's close this deal, and then we'll celebrate!" Since the celebration comes after the sale, then is correct.

Then is also often used with if. Think in terms of if-then statements: "If we don't get to the office on time, then we won't be able to close the deal today."

Than involves a comparison. "Landing Customer A will result in higher revenue than landing Customer B," or "Our sales team is more committed to building customer relationships than the competition is."

Ultimate and penultimate

I once received a pitch from a PR professional that read, "(Acme Industries) provides the penultimate value-added services for discerning professionals."

As Inigo would say, "I do not think it means what you think it means."

Ultimate means the best, or final, or last. Penultimate means the last but one, or second to last. (Or, as a Monty Python-inspired Michelangelo would say, "the Penultimate Supper!")

But penultimate doesn't mean second-best. Plus, I don't think my PR friend meant to say her client offered second-class services. (I think she just thought the word sounded cool.)

Also, keep in mind that using ultimate is fraught with hyperbolic peril. Are you -- or is what you provide -- really the absolute best imaginable? That's a tough standard to meet.

And now for the dreaded apostrophes:

It's and its

It's is the contraction of it is. That means it's doesn't own anything. If your dog is neutered (the way we make a dog, however much against his or her will, gender neutral), you don't say, "It's collar is blue." You say, "Its collar is blue."

Here's an easy test to apply. Whenever you use an apostrophe, un-contract the word to see how it sounds. Turn it's into it is: "It's sunny" becomes "It is sunny."

Sounds good to me.

They're and their

Same with these: They're is the contraction for they are. Again, the apostrophe doesn't own anything. We're going to their house, and I sure hope they're home.

Who's and whose

"Whose password hasn't been changed in six months?" is correct. Use the non-contracted version of who's, like, "Who is (the non-contracted version of who's) password hasn't been changed in six months?" and you sound a little silly.

You're and your

One more. You're is the contraction of you are. Your means you own it; the apostrophe in you're doesn't own anything.

A local nonprofit in my area once displayed a huge sign that said, "You're Community Place."

Hmm. "You Are Community Place"? No, probably not.

Now it's your turn: What words would you add to the list?