1) Brace 2) Bridge suit holding 3) Couple 4) Couplet 5) Distich 6) Duad 7) Duet 8) Dyad 9) Pair 10) Span 11) Twain 12) Twosome 13) Yoke 
(from the article `logic, history of`) ...identical.Axiom of elementary sets. There exists a set with no members, the null or empty set. For any two members of a set, there exist ...
noun (bridge) a pair of playing cards that are the only cards in their suit in the hand dealt to a player
An original holding of two of a suit.
a set of only two cards of the same suit in a hand as dealt: The other player held a doubleton.