So, this started me wondering why males and females are 'opposite'.
"Different-sex couples" sounds more correct.
What does "opposite" mean?
-tg
"Opposite-sex" has meaning in a context where there are only two
sexes. It loses it's meaning when there are more than two.
No, that's what I was questioning. Nothing about 'only two' requires
that the two be 'opposite'.
-tg
Like every common English word, it has several meanings. English
doesn't come in pills, it comes in fluffy cotton balls :-)
Mirriam-Webster's definition #4 applies here:
4: being the other of a pair that are corresponding or complementary
in position, function, or nature <members of the opposite sex>
Another example: "Chess queens are set up on squares of opposite
color."
I know your point is that the two sexes aren't contrary. Only one of
them is contrary - the [urk ack, you'll have to make up your own mind
which] :p