Term for a pair of words with opposite meanings, which together encompass everything, so that in all cases one or the other (but not both) must apply. For example:

concrete vs. abstract; animate vs. inanimate; real vs. fictitious.

  • Do you mean "antonyms"?
    – Draconis
    Oct 2, 2022 at 22:15
  • 3
    Er, none of those encompass everything. Is idleness animate or inanimate? Is love real or fictitious? Is sexuality concrete or abstract? Oct 2, 2022 at 23:17

1 Answer 1


In set theory, two disjoint sets (sets such that no element is a member of both) the union of which includes all possible elements are said to be complementary.

I believe I've heard this term used when discussing language more generally but don't have examples to hand.

I would not however say that all your examples are complementary though.

For one thing they only apply to nouns, and not all words in general (this doesn't rule them out as complementary, but it is a caveat that would need to be noted).

More significantly though some languages with animacy may have nouns that have undefined animacy. For example in Polish only masculine nouns are animate or inanimate (they may also be personal, although this could be viewed as a subclass of animate nouns).

Real and fictitious is even worse. Fictitiousness implies that the noun is a fiction deliberately created by someone, so a misconception would not be included as fictitious but is certainly not real!

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