pair

[1]	match (up) , mate , pair off/up , team (up) , put together , partner , twin , double , join , unite , yoke , wed , marry , join in wedlock/in holy matrimony
[2]	pair off , partner off , couple
[3]	match , mate , couple , twin
[4]	geminate
[5]	geminate
[6]	copulate , mate , couple

[1]	couple , brace , twosome , two of a kind , set of two , matched set , duo , dyad , twins , double , doublet , brace , span , yoke , team , tandem
[2]	couple , twosome , twain , brace , span , yoke , couplet , distich , duo , duet , dyad , duad