牙疼 literally means 'tooth pain' — 牙 (yá) means 'tooth', and 疼 (téng) means 'to ache' or 'to be painful'. Together, they form a compound that functions both as a noun ('toothache') and as an intransitive verb ('to have a toothache'). It is commonly used in everyday speech to describe dental discomfort, often sudden or severe, and rarely appears in formal medical contexts (where terms like 牙髓炎 yá suǐ yán 'pulpitis' may be used instead).

This word is frequently used in personal health conversations — for example, when explaining symptoms to a doctor, declining an invitation due to pain, or warning others about poor dental hygiene. Unlike many Chinese pain-related words (e.g., 头疼 tóu téng 'headache'), 牙疼 does not carry common figurative meanings — it refers almost exclusively to physical dental pain. It’s also a frequent topic in health education materials aimed at children and adults alike.