Hi! Good question! I'd describe curly hair as hair with "tight" curls. Wavy hair is has loose curls. You can observe the length if the hair and the tightness of the curls.
Curly hair: Tight curls, springy, shorter hair length because of the curls.
Wacy hair: Looser curls, looks the same as drawing a sound wave on a piece of paper; hair length is longer becuase of the loose curls.
I hope this helps. 🤙🏼