A sensor includes a determining circuit and an output circuit. The determining circuit receives a first signal from a pixel in response to light and outputs a second signal associated with occurrence of an event, based on the first signal. Based on the second signal being received in a time period between a first time when a third signal is received from a processor and a second time when a condition is satisfied, the output circuit outputs a fourth signal associated with occurrence of the event in the time period to the processor after the second time.