Why should there be one word? I don't think there is one. People might say 'my partner who I don't live with', I suppose, but why would they have to explain that to anyone?

@MichaelHarvey Why? For the same reason that we have a specific term for people who are married and for people who live together without being married :)

@MichaelHarvey I realise my previous comment may have seemed rude. Entirely unintended!! I think perhaps it's just a matter of cultural differences? But would you say native speakers of English would find "live-apart partner" odd/hard to understand?

I think it may be a matter of cultural or linguistic difference. 'Live-apart partner' would be understood, but would probably seem odd or suggestive of a non-native culture. An artificial expression to cover a situation that does not need such a term. Many couples would resist such categorisation. I lived with my girlfriend for 5 years, then she went to college for 3 years, and we saw each other at weekends, and she came back during vacations, and when she got her degree, we resumed living together. Domestic arrangements are not a compulsory part of a relationship description.

@MichaelHarvey Thank you for your elaboration on this! It's interesting to see how our culture affects us. To me, there's nothing artificial about this concept, and I'd say we need a term to cover this kind of situation just as much as we need a term for people who are married. In my culture, there are three main kinds of relationships: you can be married, cohabitants or live-apart partners, and I wouldn't be surprised if someone told me the two latter kinds are more common than the first. Then you can be boyfriend/girlfriend as well, but that's not a recognised category in the same way.

Is there a term like that in your language?

@gotube Indeed there is! :) And it's very much seen as an established kind of relationship :) You can be "gift" (married), "sambo" (cohabitant) or "särbo" (live-apart). These three categories would all appear in any situation where you're asked to indicate your marital status for instance.

So..... Sweden.

@MichaelHarvey Yes :)

But we 'indicate our marital status' on official forms that have a need for that information; we don't bandy it about in conversation.

@MichaelHarvey (although in Swedish, we'd use "sambo" and "särbo" in normal speech as well)

I wouldn't use 'spouse', for the same reason I would not call my cat Stripy my 'domestic feline companion animal'.

I guess the 'husband/wife' or 'partner' distinction is a valid one but that third one seems a bit odd to a Brit.

@MichaelHarvey Exactly :) (Just to be clear though: what I'm after is precisely an "official" word corresponding to "spouse" and "cohabitant", for use in official contexts such as forms and the like) (This comment was meant in answer to your comment on spouse)

@MichaelHarvey I can understand that when I think about it. To a Swede it isn't odd though :)

I can imagine a form that people complete to get state benefits might include a section asking who you live with, and the distinction between spouse/partner and sibling/friend/housemate might be relevant for calculating entitlement, but the question of, basically, who you have sex with, and where they live, doesn't seem to be on any official form that I can think of (maybe the STD clinic?).

@MichaelHarvey :))) I realise from your comments, and from James K's answer, that Sweden and the UK are very different in this... :)

In 1950s and 1960s, Anglos going to Scandinavia were perplexed at the open attitude towards sex (see e.g. 'The Prize' by Irving Wallace, where an American Nobel winner goes to Sweden and has sex with a woman he meets on a sleeper train, and is confused when she does not want to continue seeing him), but it is odd to think this attitude extends to official forms.

In my case, I call her my wife... She is still, in legal and social senses, my spouse. We just don't get to spend much time in the same country.

@MichaelHarvey There's nothing wrong or unusual about using the word "spouse" to refer to a husband or wife without specifying gender. But it does require actually being married, whereas the OP seems to be asking for a term for an unmarried couple.

@DarrelHoffman - it's kind of clunky in casual speech. Q: Who did you go to the cinema with, Mike? A: I proceeded there in a horseless carriage with my spouse.

@MichaelHarvey Right, but if you weren't referring a specific individual, or to multiple people, it's perfectly fine. e.g.: "It's common for a person to go to the cinema with their spouse." Or: "Mike, Susan, and Pat all went to the cinema with their spouses."