I freely acknowledge that, in a list of this sort, “glossary” is a fancy Latin word for a collection of pet peeves (noun, 1919), meaning an annoyance or irritation. One of my peeves is that, as a noun originating in America, it had not been admitted into the Shorter Oxford English Dictionary (1968) on my desk in London when I edited the Sunday Times. Now, it is recognised (“back-formation from peevish”). I admit I have no evidence for believing that the neglect of peeve is to blame for angering the poltergeist Peeves in the Hogwarts School of Witchcraft and Wizardry.

Affect/Effect You can only affect something that already exists. When it does, you can effect, or bring about, a change in it. To say: “It effected a change in his attitude” is correct; so is: “It affected his attitude.” To combine the two – “It affected a change in his attitude” – is silly.

Alibi Means “proof that one was elsewhere” but is confused with “excuse”, which has a wider generality. Let us save “alibi” for the precision of proving you were not within a mile of the kitchen when the last slice of apple pie vanished.

Alternatives Wrongly used for “choices”. If there are two choices, they are properly called “alternatives”. If there are more than two, they are choices. But in 2017, the tides of the expedient post-truth era sapped centuries of definition. Kellyanne Conway, a counsellor to Donald Trump, explained to NBC’s Chuck Todd that press secretary Sean Spicer’s series of falsehoods inflating the crowds at the Trump inauguration weren’t lies, they were “alternative facts”.

Anticipate Confused with “expect”. To expect something is to think it may happen; to anticipate is to prepare for it, to act in advance. To say a fiancee expects marriage is correct; to say she is anticipating marriage defames the lady.

Blatant/Flagrant It’s best to use “blatant” for offence that is glaringly obvious, without care, brazen. Best use “flagrant” to emphasise a serious breach of law or regulation.

Chronic Confused with “acute” or “severe”, medically the opposite. It means long-lasting (from the Greek chronos, “time”). An acute illness comes to a crisis; a chronic one lingers.

Compose/Comprise Compose means “to form” or “constitute”. Comprise means “to contain, include, be made up of”. The whole comprises the parts. The US comprises 50 states; 50 states do not comprise the US. After the 2014 referendum on independence for Scotland, the UK still comprised England, Scotland, Northern Ireland and Wales.

Continual/Continuous “Continual interruptions” says it all, meaning the speaker resumed his argument after the interruption. The speech was not continuous, as a river is, because the flow was broken.

Crescendo Confused with “climax”. It indicates a passage of music to be played with increasing volume. Figuratively, it means “to rise to a climax”. Thus the cliche “Rise to a crescendo” is nonsense.

Decimate Confused with “destroy”. By derivation, decimation means “killing one in 10”. Today, it is often used figuratively to mean “very heavy casualties”, but to say “completely decimated” or “decimated as much as half the town” simply will not do.

Dilemma Confused with “problem”. If you have a problem, you do not know what to do. There may be many solutions. If you have a dilemma, you have a choice of two courses of action, neither attractive.

Disinterested/Uninterested If you’re in some messy dispute, you don’t want an uninterested arbiter, judge or mediator, so uninterested he nods off. You don’t want an arbiter who has a selfish interest, declared or concealed. You want a neutral, disinterested person who cares enough for truth.

Entomb Confused with trap. The trapped miners may be alive; entombed miners are dead, ie in a tomb.

Flotsam/Jetsam Married in common parlance, but divorced in maritime law. Jetsam is stuff jettisoned, thrown overboard by the crew of a ship to lighten the load in stormy seas. If you find this stuff, it’s yours. Flotsam is cargo or wreckage floating in the sea. Flotsam is legally the property of the vessel’s owner.

Forego/Forgo: Forego means “to go before in time or place” – think of the final e in before. To forgo is to give up or relinquish.

Gourmet/Gourmand The gourmet, one with a refined, discriminating taste for the best food and wine, will be insulted to be called a gourmand, a glutton fond of good things.

Inchoate/Incoherent “Inchoate” describes something not ready to be judged “incoherent”, which means “lacking clarity”. The inchoate idea or thing is embryonic, in the early stages of being formed.

Incumbent As a noun, the current holder of an office; a “former incumbent” is nonsense. But when you hold an office, it is incumbent (adjective) on you to perform your duties.

Inflammable/Flammable Danger in a word again. The prefix “in-” might suggest that something inflammable won’t catch fire, that it is comparable to the absolutes “incapable” and “invulnerable”. But it does catch fire as easily as anything flammable, because the two words mean the same. (The prefix “in-” in this case means “into”, not “non”.)

Insidious/Invidious Both nasty, but “insidious” is evil by stealth; you don’t know the worm is in the apple. The invidious utterance or person invites odium more openly.

Judicial/Judicious Judicial means “connected with a court of law”; judicious means “wise”. Not all judicial decisions are judicious.

Less/Fewer “Less” is right for quantities – less coffee, less sugar. It means “a smaller amount”. “Fewer” is right for comparing numbers – fewer people, fewer houses; less dough results in fewer loaves. Nobody would think of saying fewer coffee, fewer sugar, but every day somebody writes “less houses”.

Litigate Did you hear what happened in the court case to make Trump release his tax returns? No? Neither did anyone else. In January 2017, while telling ABC why Trump would not keep the off-and-on promise, Conway said: “We litigated this all through the election. People didn’t care. They voted for him.” Wrong verb. To litigate is to enter a lawsuit. Better verb for the serial flip-flopping: “dodged”.

Luxuriant/Luxurious The film star can have a luxurious car that is “full of luxury”, but not a luxuriant car. That would mean the car that is producing abundantly, growing profusely, since “luxuriant” refers to something that grows.

Momentarily You have to hope the pilot and stewards are lying when they say: “We will be in the air momentarily.” That does not mean: “We will be in the air in a few minutes.” It means: “We will be in the air for a moment.” That is strictly speaking, of course, but what is the point of having words if they mean nothing?

Prescribe/Proscribe Opposite meanings. An action or product that is proscribed by authority is banned. A “prescription” is advised, recommended.

Refugee/Migrant War and terrorism in Iraq and Syria forced millions of people to flee and seek refuge in Turkey, Jordan, Egypt and western Europe, notably Germany. They were refugees, but they became migrants, unwelcome in countries that feared to admit them for security, religious or economic reasons.

Refute A strong verb, meaning “to disprove, to demonstrate falsehood”. It has been emaciated by its careless confusion with “rebut”, “reply”, “response” and, less forgivably, “deny”. A denial is merely a contrary assertion; it does not demonstrate the falsity of the assertion. Nor does “rebut”. A rebuttal is a denial dressed up in battle armour.

Regalia Regal means “of or by kings”, and regalia means “the insignia of royalty”. “Royal regalia” is therefore tautologous, and “the regalia of a bishop” is contradictory. Freemasons, however, have adopted the term for their insignia.

Replica/Reproduction Ask for your money back if you buy “a virtual replica” of the Eiffel Tower, the Parthenon or any work of art. You may have bought a good reproduction, copy, duplicate, model or facsimile, but a replica is one recreated by the original creator, so there is no such thing as “a virtual replica”. It either is or isn’t. The journalist James Kilpatrick, who manned the barricades to defend the integrity of “replica”, was cross, with reason, that the respected Smithsonian magazine offered “an almost incredibly authentic replica of the Titanic – a replica that measured 3in in length”.

Sceptic/Denier The sceptic questions the evidence; the denier flatly rejects it.

Transpire Wrongly used to mean, merely, “happen”. It comes from the Latin spirare, “breathe”. To “transpire” is to emit through the surface of leaves or skin and, figuratively, is best used for when some fact oozes out, especially a secret.

Viable/Feasible “Viable” means capable of independent life – a viable foetus or seed or, figuratively, in the sense of “capable of succeeding”, a candidate. “Feasible” means “capable of being done, accomplished” – a feasible plan.

Viral Unwelcome adjective as related to Ebola, Zika and other nasty viruses. Much desired by websites in the internet age (since 1999); an item “gone viral” has been passed person to person so many times as to seem contagious.

Virtually Incorrectly used to mean “nearly all”; eg: “Virtually all the chocolates were eaten.” “Virtually” is useful for an imprecise description that is more or less right, close enough, as good as. “He’s virtually the manager.” He does not have the title, but he manages the business.

This is an extract from Do I Make Myself Clear? Why Writing Well Matters by Harold Evans, published by Little Brown. To buy this book for £17 (RRP £20) go to bookshop.theguardian.com or call 0330 333 6846. P&P charges may apply.