"Something can either be in state A or in state B; it cannot be in both of these states simultaneously, and it cannot be in neither of them. It has to be in one of those two states". What would those two states be called with respect to each other?

For example, something can either be living or dead, it cannot be both or neither at the same time. So the property of being living or dead would be called _________ of each other. It can be called the opposites of each other but that doesn't convey the full meaning. Because "black" and "white" are "opposites", but something can be other than black and white e.g., red. So it fulfills the second condition of not being in both of the states simultaneously but doesn't suffice the first condition of being in either of those states.

For reference, it is called نقیض(Naqeed) in Arabic. There is a separate word for opposite i.e., ضد (zidd).

  • Would 'contradictions' work? For example, "So the properties of being living or being dead would be called contradictions of each other."
    – Kermit
    Oct 31, 2020 at 15:47
  • At the duplicate thread the accepted answer begins 'The OP decribes exhaustive and mutually exclusive cases'. 'Binary' is also mentioned. Oct 31, 2020 at 17:16
  • @TheIdiot1234 No. "Contradiction" doesn't convey the full meaning as "Opposite" doesn't. Oct 31, 2020 at 18:08
  • @EdwinAshworth "Binary and mutually exclusive states" sounds good. But I was looking for a single word or a compound term for this. Oct 31, 2020 at 18:09
  • “Complement” (American Heritage Dictionary, Webster's Online Dictionary) sort-of fits, but it has so many definitions, readers might not understand which one you mean unless you spell it out.
    – Scott
    Nov 25, 2020 at 5:53

2 Answers 2


It's a binary choice / decision / classification.

Within which context the two possibilities are mutually exclusive.

Idiomatically, if some issue isn't clear-cut, we might say it's not a black-and-white issue. Most written instances of not a grey area will be for this metaphoric sense - a grey area being to some extent the opposite of a binary choice issue.


Apparently there does not exist a one word term. A traditional term would be unique alternative.

  • In the throwing of a coin the unique alternative to heads is tails. Heads and tails are unique alternatives to one another.

From the SOED

alternative B. 3 Each of the components of an alternative proposition; each of two or more possibilities; the other or remaining course; a thing available in place of another.

  • There are quite a few one-word terms. Incompatible, conflicting, incongruous, discrepant, discordant, contradictory, irreconcilable, antithetical,... But "unique alternative" doesn't appear in the first 30 words listed there as alternatives to mutually exclusive. Oct 31, 2020 at 17:29
  • @FumbleFingers None of those words except "antithetical" shows that there is only one possibility; for instance there may be several possibilities that are incompatible with something. However "antithetical" is an adjective and the corresponding noun (antithesis) wouln't do for clear cut concepts (fine for love and hate)."Unique alternative" is not a word but a self explanatory term. It is a fact that this term is not in the list, yet the meaning of "mutually exclusive events" is that of "unique alternatives to one another", that is, "unique thing available in place of another".
    – LPH
    Oct 31, 2020 at 17:50
  • I don't see "unique alternative" as a particularly "self explanatory term" in our current context. For example, it's easy to find several written instances of the collocation "several unique alternatives" (obviously "several" can't have anything to do with binary choices). It's not easy to quickly establish context for many of the singular "unique alternative", but my guess is "unique" relates to one choice, not the fact of only one other. Nov 1, 2020 at 12:08
  • @FumbleFingers It seems to me that in "several unique alternatives" the word "unique" does not means "just one" but instead (OALD, 2) "very special". That second link in your comment got on my machine a strange mixture of references in both the English and the French language—only a few instances in English—and I made a new research with "unique alternative", which produced in particular—among plenty of cases all in English—this reference (not in your link) : (1/2)
    – LPH
    Nov 1, 2020 at 16:32
  • @FumbleFingers books.google.fr/… Do read the whole paragraph; you should find it an irrefutable corroboration of the contention that "unique alternative" rhymes perfectly with the idea of binary choice. (2/2)
    – LPH
    Nov 1, 2020 at 16:36

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