Learn English – Which word or phrase describes a hotel room that is a stand-alone little building

You can use roommate, housemate, flatmate and similar terms to indicate that two unrelated people live together. None of these words imply any particular relationship (unlike cohabitation, which suggests that they have a sexual relationship or partnership).

Wikipedia notes a usage difference between American and UK English:

In the UK, the term “roommate” means a person living in the same bedroom, whereas in the United States and Canada, “roommate” and “housemate” are used interchangeably regardless whether a bedroom is shared. This article uses the term “roommate” in the US sense of a person one shares a residence with who is not a relative or significant other.

Thus, you can use housemate anywhere to indicate that two people simply live in the same house. In American English, you can also call them roommates.

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esoteric

adjective

intended for or likely to be understood by only a small number of people with a specialized knowledge or interest. [Google D]