# What do you call the property of having two separate groups that make a whole?

What do you call two non-overlapping (i.e., mutually exclusive) groups that compose a whole?

Two examples:

1. Men and women (together = all humans)

2. Age ≥ 60 yrs. and age < 60 yrs. (together = individuals of all ages)

How can this property be expressed?

• In maths jargon, those are (binary) set partitionings. – Lawrence Jan 23 '18 at 16:16
• I'm unclear from your question (particularly since the edit) whether you are looking for the word to indicate that the groups make up the entire whole? If so, then exhaustive seems appropriate. – pbasdf Jan 23 '18 at 18:36
• Although neither are very common bifurcate and bifurcal are both adjectives that could describe the whole. Bifurcate is much more common as a verb. – Phil Sweet Jan 23 '18 at 21:59

Complement:

either of two parts or things needed to complete the whole; counterpart.

• Yes, "complement" if you're talking set theory and thus "complementary" if you're looking at English. jckim, don't you think that's as likely to happen as your explanation is to be clear without the mathematical symbols? Ie, to me, the question isn't about English. – Robbie Goodwin Feb 6 '18 at 23:29

'Mutually exclusive' sounds more natural than 'non-overlapping', but I would be inclined to say the (entire) group was "divided into two'.