あくび
あくび · akubi · JLPT N2 · noun
yawn
🥱 akubi sounds like ah, coo-bee: the ahh sound that opens a big yawn
Its kanji spelling is 欠伸: 欠 began as a drawing of a person with a wide-open mouth, and 伸 means stretch. So a yawn is an open mouth plus a stretch. In everyday writing the word is usually just あくび.