Today's Lexicon

It has been debated, challenged and questioned. Here is the answer:

Yeah - (yě'ə, yā'ə, yā'ə) Pronunciation Key adv. Informal Yes. [Variant of yea.]
Origin: 1900–1905

Yea - (yā) adv. Origin: bef. 900
1. yes (used in affirmation or assent).
2. indeed: Yea, and he did come.
3. not only this but even: a good, yea, a noble man. –noun
4. an affirmation; an affirmative reply or vote.
5. a person who votes in the affirmative. Indeed; truly: They have spoken, yea shouted
their reply.

Yay!- (yā) interj. Used as an exclamation of pleasure, approval, elation, or victory