Yea, yeah, and yay are three words that are commonly equated with the word yes. If you’re one of the people doing it, you would be correct roughly sixty-six percent of the time—both yea and yeah can be used instead of yes, but it’s a whole different story with yay, which is the exclamation people use to express joy.
Everyone knows what yes means, right? It’s a word that can function as an adverb and as a noun. As an adverb, it can be used to give an affirmative answer to a question, express agreement, or to introduce disagreement with a preceding negative statement. As a noun, it means a positive reply. The word yes evolved from the Old English gese, which meant “yes,” “of course,” or “so be it.” If you’d like to use yes in a sentence, you would do it like this:
“Do you remember me telling you we are practicing non-verbal spells, Potter?”
“Yes,” said Harry stiffly.
“There’s no need to call me ‘sir’ Professor.”
—J.K. Rowling, Harry Potter and the Half-Blood Prince
“Yes, Gawker Media—the corporate entity that publishes cool tech sites like Gizmodo, Kotaku, and Lifehacker; the purveyor of Jalopnik, Deadspin, and Jezebel—will survive bankruptcy in some form.” —Wired
Yea (pronounced “yay”) means yes, but you would typically use it only under specific circumstances, such as a formal vote. Voting yea means that you are in favor of the proposal. Even less commonly in modern speech, it can also be used instead of “indeed” or when you want to emphasize and reiterate something you just said. Yea is by no means a recent entry into the language—its origin can be traced all the way back to the Old English word gēa.
“The lawmaker then presses one of three buttons marked ‘yea,’ ‘nay’ or ‘present,’ and the vote is recorded.”
—The New York Times
“Woe to him who would not be true, even though to be false were salvation. Yea, woe to him who, as the great Pilot Paul has it, while preaching to others is himself a castaway.”
—Herman Melville, Moby Dick
Yeah is usually cited as yes’s less formal sister. It originated around the beginning of the twentieth century, so there are no Old English words it can be traced to. But words don’t need to have roots that reach a millennium into the past for us to use them:
“And our lady friend, she thinks life works like a fairy tale.”
“Well, that’s harmless, isn’t it?”
“Yeah, but in fairy tales, when someone dies . . . it’s just a word.”
—Terry Pratchett, The Amazing Maurice and His Educated Rodents
“Yeah, in that period, the ’60s and ’70s, he would not have been the writer whose work you’d have guessed would have become so significant—someone we’d see as describing the time we’d live in half a century later.”
Yay and yea are homophones—they are both pronounced the same. They have different meanings, though. While yea is the word we sometimes use for yes, yay is the word we use to express joy, approval, or excitement. The origins of yay are difficult to pin down—some sources say it came from yeah, other say it came from yea, and there’s always the yay used as this when we say “she was about yay tall”—any of these could be the origin of the yay we use today.
“Welcome to the latest comedy trend . . . yay, smiley face, clapping hands.”
“My brother broke into a toothy grin. ‘Yay! Your brain works!’”
—Rick Riordan, The Last Olympian
from Grammarly Blog https://www.grammarly.com/blog/yea-yeah-yay/