保暖 (bǎo nuǎn) means 'to keep warm' and is used for clothing, materials, or items that provide warmth (e.g., 保暖大衣 'thermal coat'). It differs from 取暖 (qǔ nuǎn) 'to warm oneself' (a person's action) and 供暖 (gōng nuǎn) 'to supply heating' (a building system). Unlike adjectives 暖和/温暖, 保暖 is a verb focusing on the function of retaining heat.