1. [n]  something that happens at a given place and time
2. [n]  a phenomenon that follows and is caused by some previous phenomenon; "the magnetic effect was greater when the rod was lengthwise"; "his decision had depressing consequences for business"; "he acted very wise after the event"
3. [n]  (relativity theory) a phenomenon located at a single point in space-time; the fundamental observational entity in relativity theory
4. [n]  a special set of circumstances; "in that event, the first possibility is excluded"; "it may rain in which case the picnic will be canceled"

1. \E*vent"\, n. [L. eventus, fr. evenire to happen, come
   out; e out + venire to come. See {Come}.]
   1. That which comes, arrives, or happens; that which falls
      out; any incident, good or bad. ``The events of his early
      years.'' --Macaulay.
            To watch quietly the course of events. --Jowett
                                                  (Thucyd. )
            There is one event to the righteous, and to the
            wicked.                               --Eccl. ix. 2.
   2. An affair in hand; business; enterprise. [Obs.] ``Leave we
      him to his events.'' --Shak.
   3. The consequence of anything; the issue; conclusion;
      result; that in which an action, operation, or series of
      operations, terminates.
            Dark doubts between the promise and event. --Young.
   Syn: Incident; occurrence; adventure; issue; result;
        termination; consequence; conclusion.
   Usage: {Event}, {Occurrence}, {Incident}, {Circumstance}. An
          event denotes that which arises from a preceding state
          of things. Hence we speak or watching the event; of
          tracing the progress of events. An occurrence has no
          reference to any antecedents, but simply marks that
          which meets us in our progress through life, as if by
          chance, or in the course of divine providence. The
          things which thus meet us, if important, are usually
          connected with antecedents; and hence event is the
          leading term. In the ``Declaration of Independence''
          it is said, ``When, in the cource of human events, it
          becomes necessary.'' etc. Here, occurrences would be
          out of place. An incident is that which falls into a
          state of things to which is does not primarily belong;
          as, the incidents of a journey. The term is usually
          applied to things of secondary importance. A
          circumstance is one of the things surrounding us in
          our path of life. These may differ greatly in
          importance; but they are always outsiders, which
          operate upon us from without, exerting greater or less
          influence according to their intrinsic importance. A
          person giving an account of a campaign might dwell on
          the leading events which it produced; might mention
          some of its striking occurrences; might allude to some
          remarkable incidents which attended it; and might give
          the details of the favorable or adverse circumstances
          which marked its progress.
   

2. \E*vent"\, v. t. [F. ['e]venter to fan, divulge, LL.
   eventare to fan, fr., L. e out + ventus wind.]
   To break forth. [Obs.] --B. Jonson.
   

1. An occurrence or happening of significance to a task or program, such as the completion of an asynchronous input/output operation. A task may wait for an event or any of a set of events or it may (request to) receive asynchronous notification (a signal or interrupt) that the event has occurred.

See also event-driven.

2. A transaction or other activity that affects the records in a file.