Acronym: this is a word, like radar or NATO, not a set of initials, like the BBC or the IMF.
Aetiology is the science of causation, or an inquiry into something's origins. Etiolate is to make or become pale for lack of light.
Aggression is an unattractive quality, so do not call a keen salesman an aggressive one (unless his foot is in the door or beyond).
Agony column: when Sherlock Holmes perused this, it was a personal column, not letters to an agony aunt.
Agree: things are agreed on, to or about, not just agreed.
Aggravate means make worse, not irritate or annoy.
Alibi: an alibi is the proven fact of being elsewhere, not a false explanation.
Alternate, as an adjective, means every other.
Alternative: strictly, this is one of two, not one of three, four, five or more (which may be options).
Among and between. Some sticklers insist that, where division is involved, among should be used where three or more are concerned, between where only two are concerned. (So The plum jobs were shared among the Socialists, the Liberals and the Christian Democrats, while the president and the vice-president divided the cash between themselves.) This distinction is unnecessary. But take care with between. To fall between two stools, however painful, is grammatically acceptable; to fall between the cracks is to challenge the laws of physics.
Anarchy means the complete absence of law or government. It may be harmonious or chaotic.
Anticipate does not mean expect. Jack and Jill expected to marry; if they anticipated marriage, only Jill might find herself expectant.
Apostasy and heresy. If you abandon your religion, you commit apostasy. If that religion is the prevailing one in your community, and your beliefs are contrary to its orthodoxy you commit heresy.
Appeal is intransitive nowadays (except in America), so appeal against decisions.
Appraise means set a price on. Apprise means inform.
Assassinate is, properly, the term used not just for any old killing, but for the murder of a prominent person, usually for a political purpose.
Autarchy means absolute sovereignty. Autarky means self-sufficiency.
Beg the question means neither raise the question, invite the question nor evade the answer. To beg the question is to adopt an argument whose conclusion depends upon assuming the truth of the very conclusion the argument is designed to produce. All governments should promote free trade because otherwise protectionism will increase. This begs the question.
Bellwether. This is the leading sheep of a flock, on whose neck a bell is hung. It is nothing to do with climate, prevailing winds or the like.
Between: see Among and between.
Blooded means pedigreed or initiated. Bloodied means wounded.
Bon vivant, not bon viveur.
Both...and: a preposition placed after both should be repeated after and. Thus, both to right and to left; but to both right and left is all right.
Brokerage is what a stockbroking firm does, not what it is.
