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1540s, "a word;" 1580s, "expression of ideas in words," from Late Latin dictionem (nominative dictio) "a saying, expression, word," noun of action from dic-, past participle stem of Latin dicere "speak, tell, say" (source of French dire "to say"), related to dicare "proclaim, dedicate," from PIE root *deik- "to point out" (cf. Sanskrit dic- "point out, show," Greek deiknynai "to prove," Latin digitus "finger," Old High German zeigon, German zeigen "to show," Old English teon "to accuse," tæcan "to teach").
The choice of words. Diction is effective when words are appropriate to an audience. A man might refer to his car as his “wheels” in casual conversation with a friend, but if he were writing an essay for a group of economists, he would write, “People base their decision to buy an automobile on the following considerations,” not “People base their decision to buy wheels on the following considerations.”
choice of words, especially with regard to correctness, clearness, or effectiveness. Any of the four generally accepted levels of diction-formal, informal, colloquial, or slang-may be correct in a particular context but incorrect in another or when mixed unintentionally. Most ideas have a number of alternate words that the writer can select to suit his purposes. "Children," "kids," "youngsters," "youths," and "brats," for example, all have different evocative values.