卫生 (wèi shēng) refers to cleanliness and practices that prevent disease — it's a noun ('hygiene, sanitation') or adjective ('hygienic, sanitary'). Unlike 健康 (jiàn kāng 'healthy'), which describes a person's overall physical condition, 卫生 focuses on environmental or behavioral cleanliness (e.g., food hygiene, bathroom sanitation). The related word 卫生间 (wèi shēng jiān) is a specific place: 'bathroom, toilet'.