婚姻上的一個配偶
這一支最貼近字面：-gamy 講的本來就是婚配，所以這裡的那條線是法律和習俗承認的。
noun · C1
The custom or practice of being married to only one husband or wife, as opposed to being married to several people.
一夫一妻（制）
核心畫面
The word is built from two pieces: mono- (one) and -gamy (marrying). One way to hold it is a single line drawn between two beings, and no second line leaving either of them. Whether that line is a marriage certificate or two birds returning to the same nest is what the two senses differ about; the picture of one line is the same in both.
這個字由兩塊組成：mono-（一個）和 -gamy（婚配）。可以想成兩個個體之間畫了一條線，而且沒有第二條線從任何一…更多收起
這個字由兩塊組成：mono-（一個）和 -gamy（婚配）。可以想成兩個個體之間畫了一條線，而且沒有第二條線從任何一邊拉出去。這條線是一張結婚證書，還是兩隻鳥每晚回到同一個巢，就是兩個意思分開的地方。但「只有一條線」這個畫面兩邊都一樣。From the word’s history
Wiktionary gives monogamy from French monogamie, from Late Latin monogamia, from Ancient Greek monogamía, and analyses it as mono- + -gamy. The modern word still says the same thing: one marrying.
字源資料說 monogamy 經法文 monogamie、後期拉丁文 monogamia，來自古希臘文 monogamía，並把它拆成 mono- 加 -gamy。今天的意思和當初一樣：只有一個配偶。
Wiktionary via the supplied evidence packet (kaikki:3f6f69a190036ae4:700222645:17479): 'From French monogamie ... By surface analysis, mono- + -gamy.'
Two branches
關係上的一個伴侶
同一條線，但這次不需要證書。只要兩邊都沒有第二條線，就算。
noun · C1
Having a sexual relationship with only one partner. It is used about people, and also about animals that keep one mate, sometimes for life.
單一伴侶關係