Remember President Reagan's jab at the Soviet Union as ''the focus of evil in the modern world''? That was a clear case of categoria - the direct exposure of an adversary's faults. Or was it hyperbole (an extravagant statement used as a figure of speech)?
Such rhetorical tags aren't very enlightening in any political or diplomatic sense. But they could shed some light on what Mr. Reagan - or any other wielder of language - is up to when he chooses his words. It's such classic strategies of language, dutifully labeled and cataloged, that fill the first of these three books for word lovers - Willard R. Espy's ''The Garden of Eloquence: A Rhetorical Bestiary.''
Actually, categoria and hyperbole (along with others of their ilk from actio to zeugma) literally ''people'' Mr. Espy's book. Instead of simply ticking off his linguistic luminaries, the author transforms each into a fanciful beast capable of rolling off bits of verse to illustrate its place in the rhetorical scheme of things. Epizeuxis (the repetition of a word for emphasis) is portrayed as a huge bumblebee with three sets of wings; Periphrasis (the use of many words to express the sense of one) is a horse with extra sets of legs, ears, and eyes - and two tails instead of one.
The whimsy gets a little thick after a while. But you have to admire Mr. Espy's good intentions. He's committed to reviving the study of rhetoric as the effective use of language. This discipline, he says, has been consigned to ''outer darkness'' for the last 200 years. Forerunners in his crusade include the Rev. Henry Peacham, who in 1577 compiled the original ''Garden of Eloquence, '' archetype for the present volume.
Unfortunately, Mr. Espy's fanciful approach to his subject may be better suited to a 16th-century audience than to today's readers. In any case, he does a fair job of corralling the teeming menagerie of rhetorical wildlife that hums, chirps, and gallops around us, darting out of the TV set, tumbling off the front page. Now, how to tame those beasties?
One can make a moderate start with Philip Howard's book, ''A Word in Your Ear.'' There's little whimsy here, just hard-headed, and mostly good-natured, insights into correct usage. As literary editor of the Times of London, he has daily opportunities to dig into today's malapropisms and solecisms. He's particularly alert to ''newcomers'' that sneak into the language under the guise of chic usage.
For example, Mr. Howard decries the misuse of such mathematical terms as ''parameter.'' To quote Mr. Howard, ''A lot of us mathematical dunces seem to think that it is merely an impressive alternative to a perimeter.'' But most people faced with the actual definition of the word would probably never dream of using it. He also proffers a detailed explanation of the proper use of ''exponential'' - more than enough to dissuade most of us from contributing to the, uh, marked increase in the appearance of that high-powered term. ''Forensic'' is another word he'd like to reinstall in its properly narrow niche. As any Webster's dictionary will tell you, it means belonging to, used in, or suitable to courts of adjudication. It's not, Mr. Howard reminds us, a synonym for ''scientific.'' And ''fraught.'' As he points out, until recently, things or people couldn't be simply ''fraught'' - that is, burdened with adversity. They had to be fraught with something.
He also includes a fascinating little chapter on ''ghost words,'' words that never really did exist, yet somehow found their way into a dictionary. ''Dord, '' for instance. It entered a 1934 Merriam Webster Unabridged when the printer misconstrued the capitalization instruction that should have read ''D or d.''
Like Mr. Howard's book, Rosie Boycott's ''Little Entymology of Eponymous Words'' runs just over 100 pages. It's a fun book to browse. As you might guess, she has a personal stake in her subject matter - the derivation of words from proper names. Her great-great-uncle was Charles Cunningham Boycott, a retired British Army captain who had the misfortune to be a landowner in late 19 th-century Ireland. His refusal to lower rents for some of his tenants evoked the full fury of the Irish Land League. Servants left or were driven off; local merchants shunned him. The league, casting about for a suitably populist term to describe this type of action against the gentry, decided to call it, simply, a ''boycott.''
Then there's ''cant'' - hyprocritically pious language. We can thank Andrew Cant, a 17th-century Scottish preacher, for this word. He ''had such a strange way of delivering sermons that only his local congregation had any idea of what he was talking about, let alone if he was sincere,'' explains Miss Boycott. And how about ''ham,'' that perennial term for an inept actor. It's derived from Hammish McCoullough, we are told. His troop of incomparably bad actors graced the American Midwest during the mid-19th century. And, oh yes, ''yokel,'' that usually derisive tag for a rural dweller. It can be traced to the Bohemian word for Jacob, traditionally a common name among peasants in that neck of Europe's woods.
This sampling should be adequate to convince most anyone that ''Batty, Bloomers and Boycott'' makes a welcome companion for any word fancier with a few minutes of leisure and a yen for etymological wanderings.