1) General: Happening, existing, or operating at the same time.
2) In a → space-time diagram, the points that have the same
time values. Two events that are simultaneous in one
→ inertial frame are not, in general,
simultaneous in another inertial reference frame
moving relative to the first.
→ relativity of simultaneity.
Compare → synchronous.
From L.L. simultaneus, from L. simul "at the same time" +
-taneous, abstracted from → spontaneous.
Hamzamân, from ham-, → syn- +
zamân, → time.