I think the English language needs a new word: something that describes a person who is less than an acquaintance, but more than a stranger.
It’s the person who’s child likes your dog, so you end up smiling or saying hello every now and again. Or the person who used to work in the same building who you would see in the lift now and again. Or the person who works in a local shop, who you raise your eyebrows to as you pass them on the street.
You know no details about this person – their name, their marital status, their hobbies, whether they’re a big fan of Meat Loaf – but they’re not a total stranger, and your hello or eyebrow-raise won’t be greeted with the face of someone looking at a madman.
Not normally, anyway. There was one woman who worked in a local coffee shop until a year or so ago, and she must’ve lived near me because I’d see her walking down my street fairly regularly. Always pleasant when serving me coffee, she couldn’t hide her contempt if I even attempted a half-hearted smile of recognition on the street. But that seems rare. More often than not, it’s the slightly awkward mutual smile or a quick hello.
It seems to me, that this is a linguistic blind spot when it comes to relationships: family, partner, friend, colleague, acquaintance, [new word], stranger.