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50 Words You Think Are Synonyms but Aren’t

Just because the thesaurus lists two words as synonyms doesn't mean that you can simply slot one in for the other. Learn the most common mistakes.

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Close, but not identical

The thesaurus is a very handy tool: If you’re puzzling over a word that conveys your exact meaning, or trying really hard to avoid using a commonplace word, the thesaurus gives you an instant list of options. But, while many of the words in the thesaurus can be plausibly subbed in for one another, oftentimes they don’t have the exact same thing. Here are some familiar pairs of words you might think have the same meaning, but don’t quite. Plus, find out the synonyms (and antonyms) people look up the most.

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Stalwart/stubborn

Here’s an example of two words that overlap in certain ways but aren’t synonyms at all: Both “stalwart” and “stubborn” describe a state of being unmovable. Whereas “stalwart” has a positive connotation (someone who is stalwart is steady and reliable), “stubborn” connotes a negative judgment (being stubborn implies some level of ignorance along with the steadiness). Following these grammar rules will make you sound instantly smarter.

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Obtuse/abstruse

Some people say “obtuse” when they mean “abstruse,” and this is unfortunate because “obtuse” is an insult: it means dim-witted. By contrast, “abstruse” refers to something that is difficult to understand in general. To put it another way, just because you have trouble understanding an abstruse concept doesn’t mean you’re obtuse.

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Discriminatory/prejudicial

While these two cover some of the same ground (both are adverbs describing actions that are harmful), “discriminatory” describes an action that is harmful because it unfairly draws a distinction between different categories of people or things (such as age, race, religion, or gender). “Prejudicial” generally describes an action that is harmful.

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Infertile/sterile

One who is infertile (having difficulty conceiving a child) might or might not be sterile (incapable of conceiving a child). One who is sterile will always be infertile, however.

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Factoid/trivia

The “oid” in “factoid” can make the word “factoid” appear to mean a small fact, such as a bit of trivia. However, the suffix, “oid,” means something that resembles something else. In other words, factoids merely resemble facts. They aren’t facts, at all. In fact, factoids are false facts. Here are some more surprising words that don’t mean what you think they do.

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Deceptively/actually

The problem with the word “deceptively” is that it’s a bit deceptive, so to speak. In other words, it could mean one thing, as well as that thing’s exact opposite. So while you may be using it correctly, technically, your audience may not understand what you actually mean. Still with us? For example, if you describe a house as “deceptively small,” you may mean that it’s quite the opposite of small even though it might appear small. But the person you’re talking to may believe that you’re saying the house is smaller than it appears. Check out these funny examples of how not to use a thesaurus.

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Belies versus disguises (versus betrays)

Like “deceptively,” the word “belies” causes confusion because it has two meanings that mean the opposite of one another. According to the dictionary, “belie” is a verb that means disguise or gives a false impression. For example, you may be using a smile to belie your lying eyes while some people use “belie” to mean “betray” as in “your eyes belie the malice beneath your smile.” This latter use is so common, so it’s difficult to know what someone means when they write or say “belies” instead of “disguises” or “betrays.”

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Religion/ethnicity

These two share some overlap, but they aren’t the same and can’t necessarily be used interchangeably. Your religion refers to your system of belief or worship in a higher power of some kind (usually a God or gods). Your ethnicity refers to your culturally defined identity. Here are some more “trendy” words you hear a lot but might not know the exact meaning of.

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Bisexual/pansexual

The words “bisexual” and “pansexual” both refer to a fluidity in one’s sexual preferences. But “bisexual” is defined as being attracted to both men and to women. The word, therefore, presumes that there are only two genders. The definition of “pansexual” is being attracted to both men and women, as well as people who identify as no gender or some other gender. Gender identity has led to many of these grammar rules that changed in the last decade.

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Averse/adverse

While these terms are related in origin, according to the Oxford English Dictionary, they should not be substituted for one another. Whereas “adverse” describes something that is harmful or unfavorable (such as an “adverse effect” of a drug), “averse” refers to a negative feeling about something. This confusion definitely makes sense, just like these grammatical errors even smart people make.

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Historic/historical

Historic means an important event, whereas “historical” refers to something that happened in the past. So, not all historical events are historic. Find out the middle school vocabulary words that even adults get wrong.

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Unique/special

When you tell someone you think they’re unique, you’re telling them they are one of a kind—and you can tell because of the “uni” at the beginning, which is Latin for “one of a kind.” Technically speaking, every person on earth is unique. If what you’re actually trying to say is that this person is important to you—or unusual or fascinating—go with the word “special.” Brush up on some of these synonyms that will make you a better writer.

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Cause/compel

If you wish to cause something to happen, you can compel it, which means using force or pressure. Or you can be more gentle about it, using influence, prompting, or even provocation. In other words, these words overlap, but they don’t really mean the same thing, and you wouldn’t want to compel something, when causing it would be adequate. Psst…you’re probably mispronouncing these 21 common words without even knowing it.

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Redundant/repetitive

In the U.K., people who get fired from their jobs will often be told that they’ve been made redundant. If you think this word means “repetitive,” then you’ll understandably be scratching your head. The real meaning of “redundant” is “superfluous” or “unnecessary.” Makes sense now? If further enlightenment would not be redundant for you, check out these examples of phrases we say all the time that actually contain redundancies.

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Introverted/shy

Here are two different personality characteristics that are often confused but definitely do not mean the same thing. Someone who is shy experiences discomfort when meeting new people, but someone who is introverted recharges their personal energy through individual pursuits such as reading or thinking. Fascinatingly, these 20 words are actually their own antonyms.

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Capacious/large

Whereas “capacious” refers only to the size of an empty space capable of being filled, “large” can refer to something having a lot of space inside it or something capable of filling that space. Check out these overused words that make you sound boring (and some more exciting alternatives).

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Well/good

When people say “it’s all well and good,” their words are not actually redundant. That’s because “well” and “good” cover different ground. “Well” describes actions; “good” describes things. So you can sing well, but it’s even better if the song is good.

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Will/shall

We will clear up this confusion once and for all, and hopefully, you shall pay heed:

  • The word “shall” implies something that must be done. In other words, think of shall and compel in the same way.
  • The word “will” is often used to imply what must be done, it is more correctly used to refer to a prediction of what is going to happen at a future point.
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Can/may

Surely you had this lecture in elementary school when you asked your teacher, “Can I go to the bathroom?” She likely responded that with, “Yes, you can. Now ask, ‘May I go?” Use the word “can” to refer to what is possible and the word “may” to indicate what is permissible.

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Obsolete/obsolescent

When something is obsolete, it’s out-of-date or out of use; if it’s obsolescent, it’s in the process of becoming out-of-date or out of use. So what is obsolescent today may well be obsolete tomorrow. Hopefully, these obsolescent words will never become obsolete.

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Innocent/acquitted

In the U.S. justice system, everyone is innocent until proven guilty. But, in the courtroom,  just because someone is not proven guilty doesn’t necessarily mean he or she is “innocent.” Being “acquitted” means that one has not been proven guilty in a court of law. Being “innocent” means being “blameless.” It is entirely possible to be blameworthy even if one is acquitted. Find out some confusing words that mean the opposite of what you think.

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Convicted/guilty

Just because you’re guilty of wrongdoing does not mean that you’ll be convicted in a court of law, and one who is convicted may or may not be guilty. In fact, one who has been convicted may continue to proclaim his or her innocence. The word “convicted” refers simply to what a court of law has ruled with regard to one’s wrongdoing.

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Guilt/shame

When you do something bad, should you feel guilt? Or should you feel shame? According to this study of psychological terms that people often get wrong, shame is a global negative evaluation of the self in the wake of a behavior,” whereas “guilt is a specific negative evaluation of the behavior, itself.” (As in, “I did a bad thing.”) Therefore, as Pepperdine University Professor Steven Sultanoff, PhD puts it, with shame, you think, “I did something bad, which makes me a bad person,” but with guilt, you think, “I did something bad, but I’m still a good person.” Find out the common grammar “rules” that you can safely ignore without feeling guilty.

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Amicable/amiable

“Amicable” refers to a friendliness or goodwill between people or groups. “Amiable” refers to one person’s friendly disposition. A group might have an amicable meeting, because the people there are amiable.

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Anticipate/expect

Both of these words involve a prediction of future events. However, expecting something to happen is not the same as anticipating it will happen. When we expect something, it reflects our state of mind. When we anticipate something, we are already preparing for what we expect will happen. Next, improve your linguistic smarts with this list of familiar homophones that people constantly mix up.

Lauren Cahn
Lauren has covered knowledge, history, the British royal family, true crime and riddles for Reader's Digest since 2017. Having honed her research and writing skills as an attorney in the 1990s, she became one of HuffPost's first bloggers in the early 2000s, graduated to reporting hyperlocal news in the 2010s and has been researching and writing news and features for a wide variety of publications ever since. Aside from Reader's Digest, her work has appeared in Mashed, Tasting Table, Eat This, Not That!, Grown and Flown, MSN, Yahoo, AOL, Insider, Business Insider and many others.