godan verb (-mu), intransitive verb
turn yellow; become tinged with yellow; yellow with age
Describes something gradually becoming yellowish, often due to aging, sunlight, or staining. Commonly used for paper, fabric, teeth, or leaves.
古い本のページが黄ばんでいる。
The pages of the old book have yellowed.
タバコのヤニで壁が黄ばんだ。
The walls turned yellow from cigarette tar.
More general and neutral for 'become yellow'; 黄ばむ implies a dull or stained yellowing, often with a negative nuance.
Compound of 黄 (ki, 'yellow') + ばむ (-bamu, suffix meaning 'to show signs of' or 'to become'). The suffix -bamu is found in other color-change verbs like 赤ばむ (akabamu, 'to become reddish').