In most situations, the correct spelling is yea and nay. Yay is a different word that shows excitement. Most dictionaries say that the word yay and the word yea are distinct. Only Collins English Dictionary offers yay as an alternative spelling to yea. The word yea is also different from yeah, even though they have Yeah [ jæ ] (synonym of yes, opposite of nah) is for ordinary assent; and; Yea [ jɛi ] (opposite of nay) is for formal assent during a vote. It's just that many people type yea (or even just ya) when they mean yeah. Outside of the U.S., yeh [ jɛ ] is also common. Yay. Yay is an exclamation that shows feelings such as excitement, joy, happiness, triumph, and approval. The origin is fuzzy though. opens in a new window Some dictionaries say it came from yeah, but most seem to think it evolved from the adverbial yay in the phrases yay big and yay high, but then the opens in a new window Oxford English Dictionary says that the yay in yay high probably came "Yeah" and "yah" are terms of affirmation. "Yeah" is the most common of these words, and seems to have originated sometime around the early 20th century, likely in the US. It is an adverb, and speakers often use it simply to mean "yes." People can use the term as a one-word answer to yes-or-no questions, such as "Do you want to go to the park ULi1ZA.