贴身 (tiē shēn) literally means 'sticking to the body' — 贴 (tiē) means 'to stick, adhere, or press closely', and 身 (shēn) means 'body'. Together, they describe something that fits very snugly against the skin or body, like clothing, bedding, or even relationships. As an adjective, it emphasizes physical closeness, intimacy, or personal involvement.

The term is commonly used for garments (e.g., 贴身衣服 'close-fitting clothes'), accessories (e.g., 贴身首饰 'intimate jewelry', meaning worn directly on the body), and figuratively for people or services — such as a 贴身助理 ('personal assistant') who works closely with someone daily. It carries connotations of trust, immediacy, and direct contact, but not necessarily romantic; context determines whether it’s literal (fit) or metaphorical (intimate, devoted).