trigger

A trigger is any mechanism, device, or condition that initiates a process or reaction when activated. The term is used across domains to denote an initiating event rather than a specific component.

In firearms, the trigger is the lever or button that releases the hammer or firing pin, enabling discharge. Firearm triggers vary in design, including single-action (trigger performs fewer operations) and double-action (pull performs multiple steps). Safe handling and proper maintenance are critical.

In machinery and electronics, triggers can be physical sensors, timers, or control logic that start motors, actuators, or sequences. In industrial automation, a trigger can be a signal from a sensor that begins a production step.

In computing, triggers describe events that cause automated responses. Database triggers run SQL statements in response to insert, update, or delete events on a table. Event triggers in programming or workflow systems initiate routines when specific conditions are met, such as user actions or time-based schedules.

In psychology and health contexts, a trigger is a stimulus—sensory, cognitive, or environmental—that elicits a remembered emotional or physical reaction, often related to a traumatic experience or anxiety. Awareness and coping strategies are commonly recommended.

In media and entertainment, triggers are used to start sound effects, lighting changes, or narrative cues in games and stage productions.

Etymology: the term derives from the sense of initiating a sequence, not from a single component. While triggers enable automation and responsiveness, they can complicate debugging and safety if not properly designed or documented.