触发 is a transitive verb meaning 'to trigger' or 'to set off' — typically referring to initiating an event, reaction, process, or response, often suddenly or automatically. The first character 触 (chù) means 'to touch' or 'to come into contact with', while the second character 发 (fā) means 'to emit', 'to issue', or 'to activate'. Together, they evoke the idea of physical or metaphorical contact that causes something to begin — like a sensor detecting motion and activating an alarm. It's commonly used in technical, psychological, medical, and everyday contexts involving cause-and-effect relationships.

This word carries a neutral-to-formal register and appears frequently in computing (e.g., triggering a function), psychology (e.g., triggering a memory or emotion), safety systems (e.g., fire alarms), and social situations (e.g., comments that trigger strong reactions). It implies intentionality or causality but not necessarily human agency — natural events or design features can also trigger outcomes. Unlike casual synonyms like 引起, 触发 suggests immediacy, mechanism, or system-level activation.