When I talked about a relative and his パートナー visiting for Christmas, the person I was speaking to asked if his パートナー was male. Is this a common interpretation of パートナー? Is there a better word than パートナー to talk about a long-term opposite-sex partner who isn't married?
ガールフレンド was suggested, but in English, "girlfriend" wouldn't be a good choice of words as it tends to be used for short-term relationships, especially involving teenagers.