Duo and Doubleton

Duo noun - Two things of the same or similar kind that match or are considered together.

Doubleton and duo are semantically related. In some cases you can replace term "Doubleton" with "Duo", this nouns are similar.

Doubleton noun - (bridge) a pair of playing cards that are the only cards in their suit in the hand dealt to a player.

Duo and doubleton are semantically related. You can use "Duo" instead a noun "Doubleton".