Dears what word shall be used for saying that two events must not take place at same time? For example to say that two machines in a room must not simultaneously work. One shall run only after other one turned off.

closed as off-topic by Nigel J, Xanne, Hot Licks, Dan Bron, jimm101 Dec 3 '17 at 1:59

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  • What was the answer deleted? Check a good dictionary. – Kris Nov 27 '17 at 12:22
  • Never use the word dear like this. Ever. – tchrist Nov 27 '17 at 13:06
  • @tchrist - The use of "dear" in that sense is very common in subcontinent English (i.e. Pakistan/India/Bangladesh). It may be wrong for US/UK/etc. but it appears to be standard there. – SonOfPingu Nov 27 '17 at 13:47
  • Google antonym simultaneous – Hot Licks Nov 27 '17 at 14:05

If the second machine only ever runs after the first has completed its work you could describe their operation as sequential. Otherwise I think exclusive is the better choice.


I don't think there's a word or stock phrase that unambiguously captures that idea, but you might say that the two machines have mutually exclusive operation: neither can run while the other does.

  • Mutually exclusive implies one does NOT run if the other has. – moonstar Nov 27 '17 at 13:40
  • 1
    @moonstar2001 - Not true. – Hot Licks Nov 27 '17 at 14:07

The two best words for this sentence in my mind are

The two machines must be used non-simultaneously.


The two machines must be used asynchronously.

“Non-simultaneously” is a perfectly good word that has definitions in the Collins and Oxford English dictionaries (though not in Miriam Webster).

I’m not sure why moonstar thinks that “asynchronously” requires randomness. Miriam Webster defines it as “not simultaneous or concurrent in time“ and the OED defines it as “Not existing or occurring at the same time.”

“Synchronously” is also a word you can use, and is a synonym for “simultaneously.”

  • @downvoter I would love feedback on why you don’t like this answer. – Stella Biderman Nov 27 '17 at 14:35
  • A user who commented on a now-deleted post said "In engineering, to say that two processes are asynchronous doesn't mean that they cannot run at the same time: it means that one starts the other but doesn't need to wait for the other to finish before it proceeds" Not being an engineer myself, I cannot say if their observation is pertinent or not but it might explain the DV. – Mari-Lou A Dec 1 '17 at 20:30
  • @Mari-LouA That’s true, but it’s a specific technical use and not the standard usage of the term. – Stella Biderman Dec 1 '17 at 20:31
  • It seems to me that the OP is asking a specific technical question. I only wanted to relate another user's comment to an almost identical answer, deleted before you posted, that seemed relevant to your case. – Mari-Lou A Dec 1 '17 at 20:33
  • @Mari-LouA Fair. – Stella Biderman Dec 1 '17 at 20:34

There isn't one single antonym. Depending on the context you may use :

  1. Sequential (if it is one after another)

  2. Asynchronous (if events occur at random points of time)

  • Your definition of asynchronous is wrong. – Stella Biderman Nov 27 '17 at 14:36
  • thanks everyone. for me "non-simultaneous" works good. i just see it is very uncommon word. – Enkhamgalan Bold Dec 4 '17 at 1:13

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