αὐδάν

From LSJ

Γελᾷ δ' ὁ μωρός, κἄν τι μὴ γέλοιον ᾖ → The fool laughs even when there's nothing to laugh at

Menander

French (Bailly abrégé)

dor. p. αὐδήν, acc. de αὐδή.