# Trigger Events Editor

Trigger events fire when the trigger predicate changes value from false to true. This predicate is a Python expression that may involve species amounts, compartment sizes, parameter values, and the time. The triggers for each of these events are checked following the firing of any reaction of the execution of any event, and also before recording the state at a frame. The following are examples of trigger predicates.

    x > 10
    x <= 5 and t > 10

If the delay is nonzero, then this value indicates the time that will elapse between the triggering and the execution of the event. Leaving this field blank indicates a zero delay. The `TT` field stands for Trigger Time. If it is checked, then the assignments will be evaluated at the trigger time instead of the execution time.