Definition - Your choice of words, as well as the way you say them.

Example -
William F. Buckley would say eirenic, whereas the average English speaker says peaceful.
Note: When he was asked to explain this diction decision, Buckley replied that he preferred the extra syllable.

Etymology -
The word derives from the Latin dicere, to say.

Oxford English Dictionary -
Its first citation in this sense is from 1700:
"The first beauty of an Epick poem consists in diction, that is, in the choice of words and harmony of numbers."
(Dryden, Fables Pref. (Globe) 496)

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