Interjection (kandoushi)
yes; yeah; uh huh
「コーヒーのお替わりいる？」「うん、ぼくのは少なめ、弟のには多めについでね」"Do you want another cup of coffee?" "Sure, make mine on the small side but be generous with my brother's." hum; hmmm; well; erm; huh?
oof
moan or groan (of pain)
Also written ウン、うむ、ううむ、う～ん、うんっ、ウ〜ン