coincidence

(noun) an event that might have been arranged although it was really accidental. Synonyms: happenstance.

(noun) the quality of occupying the same position or area in space. Example: "He waited for the coincidence of the target and the cross hairs."

(noun) the temporal property of two things happening at the same time. Synonyms: concurrence, conjunction, co-occurrence. Example: "The interval determining the coincidence gate is adjustable."