So I've done about thirty seconds of research into the topic, and none of them were reading sci fi romances where the relationship did not end in marriage by the end of the book. I have a couple, Zan and Miranda, who begin dating in the first novel and are still in the 'dating' phase of their relationship in the second novel. I'm not sure yet if they'll ever get married, given certain...plans that I have for them. But I'm a little confused about how to call them. The terms 'boyfriend' and 'girlfriend' came into use in the first World War, and therefore sound very modern to my ear; much in the same way I would try to avoid calling something 'cool' or 'pretty' in high fantasy, I'd avoid using those words, too. Still, 'lover' just doesn't sound like quite the same relationship, even though they basically mean the same thing. However, for sci fi, I oddly enough have the same problem. 'Car' and 'boyfriend' both sound too modern for a future society. Now, I know that as an author, whatever I say is normal will be accepted as normal; suspension of disbelief is a wonderful thing. But using 'lover' in a sci fi book seems just as anachronistic as 'boyfriend'. 'Consort' could work, with the right person and relationship dynamic, but having that be my boy/girlfriend stand-in just doesn't work. My question is, how do novels set in the distant future generally handle ongoing non-marital relationships, linguistically speaking? Using modern words seems wrong, but using antique words seems even worse.
If it's the distant future, then modern terms would be old fashioned, wouldn't they? But I'd probably go with something classic like partner, paramour, comrade, accomplice, perpetual convive, et cetera. Or make up your own.
You're right that they'd be old fashioned in this new time period, but here's the thing; readers will, for the most part, accept whatever I decide is the new normal. If I decide to use boy/girlfriend, they'll probably go with it; it's more a question of 'is this all in my head or have i stumbled upon a true conundrum?' If I can't convince myself that boy/girlfriend is alright, I'll probably end up with 'partner', but that seems...i dunno, clinical? I've heard LGBT people use the word to describe their significant others, but I've never heard straight people use it the same way. disclaimer: that was purely anecdotal.
Or you could lean into the old fashioned and use words like beau or swain brought back by some future pop culture phenomenon.
"This is my couple, Miranda." Yes, perfect, no flaws. I will probably use that to refer to them as a unit, though.
IDK. Pair, duo. Interface compatible persons? I have never dealt with that problem when it comes to romance in Sci-fi. Skipping such labels, and avoiding making up some random futuristic sounding word for people in a relationship. I prefer to show it all through interactions between the parties, and their personal thoughts about the other. The whole 'show don't tell' thing.