1.
cohabitation, living together (as an unmarried couple)
An unmarried romantic couple sharing a residence. In Japanese society, this term specifically implies a romantic partnership rather than simply being roommates.
二人は同棲を始めた。
The two of them started living together.
結婚前に同棲するカップルが増えている。
More and more couples are living together before getting married.
彼女と同棲して初めて、生活習慣の違いに気づいた。
It wasn't until I moved in with my girlfriend that I noticed the differences in our daily habits.
COMMON COLLOCATIONS:
- 同棲を始める (start living together)
- 同棲生活 (life of cohabitation)
- 同棲相手 (live-in partner)
- 同棲を解消する (end cohabitation, move out)
While becoming more socially accepted, cohabitation before marriage still carries some stigma in traditional contexts in Japan. The word specifically implies a romantic relationship — for non-romantic shared living, 同居 or ルームシェア is used instead.