名詞 foursome:

1. four people considered as a unit
   同義詞：quartet, quartette
2. the cardinal number that is the sum of three and one
   同義詞：four, 4, IV, tetrad, quatern, quaternion, quaternary, quaternity, quartet, quadruplet, Little Joe

1. Let's make (up) a foursome and go out to a restaurant.
   咱們四個人(兩對男女)一起下飯館吧。

four.some

n.（名詞）
A group of four persons or things, especially two couples.
四人一組：四人或物一組，尤指兩對
Sports Games
【體育運動】 【游戲】
A game, especially a golf match, played by four persons, two on each side.
四人對抗賽：四人玩的游戲，尤指高爾夫球賽中的雙打，每邊兩人
The players in such a game.
對抗賽的四人：參加此種游戲的人

來源：
Middle English four-som
中古英語 four-som
from Old English fôowra sum [one of four]
源自 古英語 fôowra sum [四人中的一個]
fôowra [genitive pl. of] fôower [four] * see four
fôowra [] fôower的所有格復數(shù) [四個] *參見 four
sum [one] * see -some 2
sum [一個] *參見 -some2