“同X”，如“同志”、“同胞”、“同行”、“同伴”、“同路人”、“同学”等，英语各有各的译法（如 “comrade”，“compatriot”, “colleague” , “partner”， “fellow traveller”，“schoolmate”等），很难定型。但有个例外，即“同学”之译作“schoolmate”用公式表示，该是“同 x”与 “-mate”了。

就从“同学”说起吧，“同学”而又同一个班级的，英语便是“classmate”。

“同室”，则是“ roommate”：

1. His suspicion piqued by seeing me home at this hour, roommate Viktor peers at ray table.

                                                   —George Feifer: Moscow Farewell, NY 1976，p.182

与自己同住一个“flat”，就是“flatmate”：

2. Tessa's flatmate would be, I reckoned, something of a Whatcombs street type …

                                                   —Geoggrey Household: Red Anger, 1975, p.95

“同桌”则为 “table（或 desk）mate”：

3. My tablemates nodded with approval.

                                                   —Leona & Jerrold Schecter: An American Family 

                                                      in Moscow, NY 1975, p.329

“同座”为 “seatmate”：

4. On a bus I overheard two passengers discussing the value of exercise. “I bought myself a bicycle，”stated the first man.

“Do you use it much?”inquired his seatmate.

“同睡一个床的”是 “bedmate”；“（在教堂里）同坐一条板凳的”是“pewmate”；“（动物）同窝的崽子”是“littermte”：

5. Your tablemate, proposing to be your bed-mate，is a plant — I do believe.

                                                  —Thomas S. Burns: Tales of ITT, 1974, p. 46

6. My pewmate was an elderly man who had long been Mo-an's [name of a Christian church in Shanghai] pastor.

                                                 —National Geographic, July 1980, p.33

7. At that stage young cheetahs are nearly full grown and are fairly competent hunters, though they still have much to learn. Perhaps partly for that reason littermates tend to remain together for at least several more months before going their separate ways.

                                                —National Geographic, May 1980, p.728

英语中“-mate”型的合成词比较多，而汉语中往往没有现成的对应词可供汉译之用，如下列这句中的 “phonemate”就是指经常利用电话（聊天等）的谈伴：

8. This time, the wife of former Attorney General John Mitchell is telling phonemates that her husband is trying to force her out of her New York apartment“to make room for Nixon …so that he can run for Mayor of New York in 1977”.

                                               —Newsweek, September 17, 1975 as per The 

                                                  Study of Current English, December 1975, p.45