1. (noun) a single object (as distinguished from a pair)

• 1
• ace
• i
• one
• single
• unity

2. (noun) a set containing a single member

• set

3. (noun) the playing card that is the only card in a suit held in a bridge hand as initially dealt

• playing card

1. (noun) a single object (as distinguished from a pair)

• fellow
• mate