The word "哎呦" is formed by combining two characters that are primarily phonetic and function as interjections: "哎" (āi), which is used to express attention or dismay, and "呦" (yōu), which conveys surprise or pain. Together, they create a compound interjection that directly mimics a vocal exclamation, resulting in a term used to express sudden physical or emotional reactions such as pain, shock, or regret. This formation is based on sound imitation rather than morphological or semantic composition.