不能 (bù néng) is a two-character verb meaning 'cannot' or 'unable to'. It expresses inability—whether physical, mental, logical, or situational—and always precedes a verb or adjective. The first character 不 (bù) is the standard negator for verbs and adjectives, while 能 (néng) means 'to be able to' or 'can'. Together, they form a fixed negative modal verb construction, not a simple negation of 能 alone. Unlike English 'can't', 不能 cannot stand alone as a complete sentence—it must be followed by another verb (e.g., 吃, 去, 理解) or an adjective (e.g., 高, 安静).

This expression is neutral in register and used widely in both spoken and written Chinese. It conveys objective or general inability (as opposed to 不行, which often signals refusal or impracticality). It’s commonly used in daily communication—for example, explaining limitations, setting boundaries, or describing restrictions due to rules, health, or circumstances.