Diction
A writer’s specific choice of words and the style those choices create.
Diction covers the vocabulary a writer selects—formal or casual, plain or ornate, concrete or abstract—and the effect it produces. Writers shape diction to set tone, reveal character, and fit their subject. The same idea can feel utterly different depending on the words chosen to carry it.
Example
Huck’s plain, ungrammatical diction makes his voice sound authentically young and unschooled, coloring the whole narration.
The Adventures of Huckleberry Finn · Mark Twain