simultaneity

/ˌsaɪməltəˈniːəti/
noun
  1. The fact of two or more events happening at the same time.
    • The simultaneity of the two explosions suggested they were connected.
    • In physics, the simultaneity of events can depend on the observer's frame of reference.
    • The simultaneity of the meetings made it impossible for her to attend both.
Antonyms