pair; couple; antithesis; counter for items that come in pairs; counter for sets (of clothes, small furniture, utensils, etc.)
to form a pair; to pair up
annihilation (of particle and anti-particle)
to act as an opposite; to form a counterpart; to act as a twin
left-and-right pair; symmetrical pair
kanji compound formed of opposing elements; antonym; conversation (face-to-face)
couplet (Chinese poetry); pair of hanging scrolls
electron pair; Cooper pair
unshielded twisted pair; UTP
to form a pair; to correspond