Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
yeah, yup, yeh (adv.)
are some of the conventional spellings for these Conversational substitutes for yes, each reflecting a pronunciation. Yeah is the most widely used spelling, just as YA and YA-uh are the most widely heard pronunciations. The word occurs only in relatively relaxed speech—Casual and Impromptu levels, typically—and in written imitations of it.
