卫生 (wèishēng) literally combines 卫 (wèi), meaning 'to guard' or 'to protect', and 生 (shēng), meaning 'life' or 'living'. Together, they convey the idea of 'protecting life' — hence its core meaning: hygiene and sanitation. It refers to practices and conditions that preserve health and prevent disease, such as handwashing, clean water, proper food handling, and waste disposal.

This word is commonly used in both everyday and formal contexts — from school posters about handwashing ('讲卫生') to government policies ('公共卫生', public health) and hospital signage ('卫生许可证', hygiene license). While it can function as a standalone noun ('注意卫生' — pay attention to hygiene), it also appears in compound terms like 环境卫生 (environmental sanitation) or 食品卫生 (food hygiene). It carries a neutral-to-formal register and is rarely used in casual slang.