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cohabit
cohabit 是不及物动词，后面不能直接接宾语。
They decided to cohabit after dating for two years.
他们恋爱两年后决定同居。
同居
cohabiting — present participle of cohabit
先理解核心含义，再看它在真实句子里的用法。
同居
to live together as a couple without being married
They decided to cohabit after dating for two years.
他们恋爱两年后决定同居。
同居,尤指未婚但有浪漫和性关系
To live together with someone else, especially in a romantic and sexual relationship but without being married.
共存于共同环境
To coexist in common environs with.
与对立政党合作
To cooperate with an opposing political party.
cohabit
Base
原形
cohabits
3rd person
第三人称单数
cohabiting
-ing
现在分词
cohabited
Past
过去式
cohabited
Past participle
过去分词
They cohabit in a small apartment downtown.
他们在市中心的一间小公寓里同居。
Right now, she is cohabiting with her boyfriend in Beijing.
她现在正和男朋友在北京同居。
They have cohabited for five years without getting married.
他们已经同居五年，没有结婚。
cohabit 常指未婚伴侣同居，为不及物动词；如需说明对象，可与 with 连用。
They decided to cohabit before getting married.
他们决定在结婚前同居。
The couple have cohabited for five years and now plan to buy a house together.
这对夫妇已经同居五年，现在打算一起买房子。
They are cohabiting in a small apartment near the station.
他们正在车站附近的一间小公寓里同居。
cohabit 是不及物动词，后面不能直接接宾语。
They decided to cohabit after dating for two years.
他们恋爱两年后决定同居。
用 with 引出同居对象。
She has cohabited with her partner for five years.
她和伴侣同居五年了。
Not this
They cohabited each other for two years.
Use this
They cohabited with each other for two years.
cohabit 是不及物动词，不能直接接宾语；表示“和某人同居”时要用介词 with，所以 each other 前必须加 with。
Not this
Their cohabit lasted only a year.
Use this
Their cohabitation lasted only a year.
cohabit 是动词，不能作名词；表示“同居”这个行为或状态要用名词 cohabitation。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
与某人同居
He has been cohabiting with his partner for two years.
他与伴侣同居已有两年。
婚前同居
Many couples cohabit before marriage to see if they are compatible.
许多情侣婚前同居，看看他们是否合得来。
同居情侣
The couple next door are a cohabiting couple.
隔壁的这对是同居情侣。
开始同居
After dating for a year, they started cohabiting.
约会一年后，他们开始同居。
Use cohabiting naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
co-共同 + habit习惯：同居就是两人共同生活、习惯彼此。
语域：formal 常见场景：法律文书、正式报道、学术讨论 cohabit 比 live together 更正式，多用于法律、正式报道或书面语；日常口语中更常说 live together。
与 cohabit 真正押韵的有 habit、inhabit、rabbit（结尾读 /hæbɪt/ 或 /bɪt/）。注意 exhibit、prohibit 拼写以 -hibit 结尾，但读作 /hɪbɪt/，与 cohabit 的 /hæbɪt/ 不押韵，是易混淆的形近词。
Dictionary facts from ECDICT, WIKTIONARY.