Abjure and Adjure

Abjure means to "renounce" or "repudiate." Adjure means "request earnestly." The words have little in common other than their rarity and similarity of spelling, so they should not be confused.

Adopted and Adoptive

Adopted and adoptive both mean "acquired through adoption," but they are not synomyms. One is the reciprocal of the other. A child with adoptive parents is adopted; parents with an adopted child are adoptive. The difference lies in who is doing the adopting. The parents adopt the child, so the child is adopted. The child is adopted by the parents, and so the parents are adoptive.

Adverse and Averse

Adverse means "antagonistic." Averse means "feeling disclined." The word averse is more recognizable in two more commonly used forms: avert and aversion.

Affect and Effect

These words are commonly confused, and the rules given to tell them apart are often wrong. Affect means "to influence" or "to produce an effect in." Effect means "consequence" or "that which is produced by an agent or cause."

Many try to differentiate between the two by saying that affect is a verb, while effect is a noun. Unfortunately, it's not so simple. The word affect can also serve as a noun, meaning "observed or expressed emotional response," and the word effect can also serve as a verb, meaning "to become operative" or "to carry out," as in, "to effect changes."

Aggravate and Annoy

Aggravate means "worsen." Annoy means "bother" or "exasperate" or "provoke." Many speakers and writers use aggravate to mean "annoy." Although aggravate has been used in this manner for four hundred years, considerable controversy over this use exists today. Some contend that using aggravate to mean anything other than "worsen" compromises the effectiveness of the word by blurring the distinction it has from similar words. Others argue that annoy can be said to mean "worsen one's temper," which suggests that aggravate is not so inappropriate to use as a synonym for annoy after all. My recommendation is to understand that aggravate means "worsen" and not "bother," but then feel free to use aggravate in contexts where it would be taken to mean "worsen one's temper" rather than "bother" or "irritate."

Allude and Refer

Allude means to refer to something indirectly or covertly. Refer, without qualification, implies referring to something directly, by naming. Frequently allude is misused to mean "refer directly," but this is an abuse of an otherwise useful, specific word.

Anxious and Eager

Anxious means "troubled" or "worried." Eager means "having keen interest" or "impatient expectancy." When anxious is used to describe someone's expectancy, it is often incorrectly used to mean "eager," which has a far more positive connotation. One may be anxious about an impending report card, but one would be eager to go on a long-awaited vacation.

Chafe and Chaff

Chafe means "to make sore by rubbing" or "irritate or annoy" or "become annoyed." Chaff means "tease good-naturedly." Consequently, one should not become confused with the other.

Compliment and Complement

Compliment is a "remark of praise." Complement is "something that completes." Note that free refreshments are complimentary; the word refers to the phrase "with our compliments."

Continual and Continuous

Both continual and continuous describe an action or process that occurs over a long period of time. Continual, however, permits that the action may be interrupted by short breaks. Continuous means that the action never pauses. We live continuous lives, eating and sleeping continually.

Deserts and Desserts

Most English speakers understand that deserts, with the accent on the first syllable, are a dry, arid lands, while desserts, with the accent on the second syllable, are a sweet things to eat after a meal. What is often confused is that when one gets what one is deserves, good or bad, one is getting one's "just deserts," accent on the second syllable but spelled like the dry, arid lands.

Discomfort and Discomfit

Discomfort means "uneasiness or hardship" and "make uncomfortable." Discomfit means "disconcert" and "defeat; thwart." Discomfort comes from Middle English, from the Old French word desconfort. Discomfit comes from the Middle English word discomfiten, from the Old French word desconfit.

Discrete and Discreet

Discrete means "discontinuous" or "individually distinct." Discreet means "judicious." The words are understandably often confused, but they should remain distinct.

Effective and Effectual

Effective means "producing an effect" or "in effect." Effectual means "producing a desired effect." A law that is effective is only effectual when it is enforced.

Energize and Enervate

Energize means "give energy to," while enervate means "to cause to lose vitality or energy." Sometimes enervate is mistakenly believed to mean "energize," and this is a grievous error, as enervate is actually an antonym of energize.

Enormousness and Enormity

Enormousness means "largeness" or "immensity." Enormity means "depravity" or "wickedness" and also means a "crime" or "error." Frequently the word enormity is mistaken to mean "enormousness," which it does not. The two words do originally derive from the same Latin word, enormis, with the word enormity being derived through the French word enormite, but the distinction between the two English words has existed for hundreds of years.

Flack and Flak

Flack is a noun that means "press agent" or "publicist" and a verb that means "to act as a press agent." Flak is a noun that means "anti-aircraft artillery" or "bursting of shells fired form anti-aircraft artillery" or, more commonly, "excessive or abusive criticism" or "dissension, opposition." If you criticize someone, you are giving them flak, not flack.

Flaunt and Flout

Flaunt means "display ostentatiously." Flout means to "disobey openly and scornfully" or "show contempt for." Some use one for the other, but confusing the two words is still widely seen as an error and best avoided.

Forcible and Forceful

Forcible means "accomplished by force." Forceful means "powerful and vigorous." Something that is forcible can be accomplished with forceful effort.

Fortuitous and Fortunate

Fortuitous means "happening by chance" or "accidental." Fortunate means "lucky." A fortuitous event may be, but is not necessarily, a fortunate event.

Founder and Flounder

Founder means "to fail completely." Often it is used to refer to a ship, in which case it means, "to fill with water and sink." Flounder has a less severe definition; it means "to move clumsily or with difficulty" or "to make mistakes or become confused." Although the two words are similar in spelling, they are derived from different sources. Founder comes from the Latin word fundus, meaning "bottom." Flounder comes from Middle English, from the Anglo-Norman word floundre, of Scandinavian origin. We can flounder but recover, but when we founder, it's final.

Full and Fulsome

Fulsome is sometimes mistaken as a synonym for full or fullest, when, in fact, its meaning bears no resemblance to full whatsoever. Fulsome means "cloying, excessive, and disgusting." Although both words have similar etymological roots, the English definitions are divergent enough to cause some gross misunderstandings when the words are confused, particularly in incorrect expressions such as "fulsome praise" and "fulsome apologies."

Gambit and Gamut

Gambit is a strategic maneuver. Gamut is a full range or extent.

Imply and Infer

Imply means to "hint or suggest without stating directly." Infer means "reach an opinion from facts or reasoning." The two terms are sometimes mistaken to be interchangeable. In actuality, they are quite distinct. The sender of an indirectly stated message is doing the implying, while a receiver that reasons what the message is is doing the inferring.

Inanity and Inanition

Inanity means "foolishness" or "senselessness." Inanition means "lacking vigor."

Incredulous and Incredible

Incredulous means "unbelieving" or "skeptical." Incredible means "unbelievable" or "hard to believe." If something incredible happens, you may be incredulous.

Ingenious and Ingenuous

Ingenious means "clever and inventive." Ingenuous means "open, frank, and sincere" and also "naive, unsophisticated." The words have similar origins, hence the similar spelling, but their meanings have been distinct for centuries.

Insulate and Insolate

Insulate means "to cause to be in a detached or isolated position" or "to prevent passage of heat, electricity, or sound into or out of." Insolate means "to expose to the sun's rays."

Lightening and Lightning

Lightening refers to something illuminating or brightening. Lightning is what is accompanied by thunder during storms.

Loath and Loathe

Loath is an adjective, meaning "disinclined" or "reluctant." Loathe is a verb, meaning "feel hatred or disgust for." Confusion often arises about not only what they mean but how they are pronounced. Loath has a soft th sound, while loathe has a hard th sound.

Luxurious and Luxuriant

Luxurious means "supplied with luxuries." Luxuriant means "growing profusely." Some consider it acceptable to use luxuriant to mean luxurious, but the best policy is to keep the words distinct.

Mucous and Mucus

Mucous is an adjective, as in, "a mucous gland." Mucus is a noun, as in, "There is mucus emanating from my mucous glands."

Nauseous, Nauseated, and Nauseating

Nauseated means "caused to feel nausea." Nauseating means "causing to feel nausea." If you are nauseated, it is because something else is nauseating. There is no controversy about the meaning of these words, but there is much controversy over what nauseous means. Commonly, the word nauseous is used to mean "nauseated," but some maintain that it should only ever be used to mean "nauseating." In actuality, the word nauseous has meant both for over 400 years, and there is little reason to dispute an accepted usage of a word that dates back to the times in which the English language was at the summit of its development.

Niggard and N***er

The word niggard, which means "miser," and its adjective form niggardly, have fallen under attack in recent years due to the relatively recent appearance of n***er, the similarly-spelled racial slur against African-Americans. The objection to the use of niggard on grounds of racial discrimination is unfounded. Apart from the similar spelling, the two words have nothing to do with each other. Historically and etymologically, the two words have had no relation; one did not derive from the other. Niggard comes from Middle English, which in turn comes from the Scandinavian word nig. The racial slur is a much more recent word, originating from the Middle French word negre, from the Spanish word negro, from the Latin word niger. These early variations were not considered racial slurs; the derogatory connotation only started showing up as recently as the mid-1900s.

Noisome and Noisy

Noisome means "harmful" or "offensive" or "disgusting." Obviously it does not share any shade of meaning with noisy, and so the two words should not be confused with one another.

Passable and Passible

Passable means "capable of being passed." Passible means "capable of feeling or suffering; susceptible of sensation or emotion; impressionable."

Passed and Past

Passed is a past tense verb. Past can be a noun, adjective, adverb, or preposition -- never a verb.

Peccable and Peccant

Peccable means "capable of sinning." Peccant means "guilty of sinning."

Perspicacious and Perspicuous

Perspicacious means "having or showing insight." Perspicuous means "easily understood" or "lucid," or, when referring to a person, "expressing things clearly."

Practicable and Practical

Practicable means "usable," while practical means "useful." Not all practicable things are practical, and not all practical things are practicable.

Sanguine and Sanguinary

Sanguine means "hopeful" or "optimistic" or "confident." Sanguinary means "bloody" or "murderous." Obviously these are two words it's better not to confuse, lest you convey entirely the wrong idea about something.

Stanch and Staunch

Stanch is a verb that means "restrain a flow." Staunch is an adjective that means "firm in attitude, opinion, or loyalty." Both words are pronounced the same way. The distinction is actually quite recent; a hundred years ago, the two words were treated as interchangeable spelling variants. Such is no longer the case, so it's important to distinguish one from the other.

Stationary and Stationery

Stationary is an adjective that means "not moving." Stationery is a noun that means "writing paper and envelopes."

Titillate and Titivate

Titillate means "stimulate pleasantly" or "tickle." Titivate means "adorn" or "spruce up." The similarity in spelling is coincidental. Titillate comes from the Latin word titillare, which means "tickle." Titivate is a newer word which comes from the earlier word tidivate, which is likely derived from the words tidy and elevate.

Tortuous and Torturous

Tortuous means full of twists and turns. Torturous means "causing or involving torture or suffering." These words are sometimes confused because of their similar spelling, but there is no further similarity.

Turbid and Turgid

Turbid means "unclear, obscure, confused, disordered" and, when referring to liquids, "muddy, thick, unclear." Turgid means "enlarged, swollen" and, when referring to language, "pompous, overblown grandiloquent." Because the two words are relatively uncommon, one is often confused for the other. Turbid comes from the Latin word turbidus, meaning "disordered," from turba, which means turmoil, possibly from the Greek word turbe. Turgid comes from the Latin word turgidus, from turgere, which means, "to be swollen."

Venal and Venial

Venal means "open to bribery" and "corruptible" and, when referring to conduct, "influenced by bribery." Venial means "pardonable," when referring to a fault or sin, and "trifling, not serious" when referring to misconduct.