singleton
/ˈsɪŋgltən/noun
1- a single person or thing of the kind under consideration单独的人（或物体）：
splitting the clumps of plants into singletons.
将一丛植物单个分开。
1.1
- often as modifier a child or animal born singly, rather than one of a multiple birth单生子女; 单生幼畜：
singleton boys.
单生子。
1.2
- a person who is not married or in a long-term relationship单身的人; 无长期亲属关系的人。
1.3
- (in card games, especially bridge) a card that is the only one of its suit in a hand（纸牌戏, 尤指桥牌）单张（一手牌中某花色的惟一一张牌）。
1.4
- Mathematics & Logic a set which contains exactly one element【数, 逻】单元（素）集。
词源
late 19th cent.: from SINGLE, on the pattern of simpleton.