I frequently run into the situation where I'm trying to describe how well I know someone. It's hard! So I came up with "Personal Relationship Levels" (like Technology Readiness Levels) as a solution. (This is mostly just for fun, I don't expect everybody to adopt this)

PRL 0 is a complete stranger. PRL1: A second degree connection. You know of this person and know who you know who knows them. PRL2: Brief interaction. People you have met once, briefly, and maybe don’t even remember meeting.

PRL3: A distant acquaintance. People you have one or two substantive interactions with who you suspect would also remember a few things about you and be more predisposition to you than a stranger. You put some effort into emails to these people.

PRL4: Acquaintance. Someone you’ve interacted with several times, probably not 1-1. These are the people you see semi-regularly at professional events or friend’s gatherings but don’t seek out or see 1-1.

PRL5: Friendly Acquaintance. Someone you see regularly and have met with 1-1 but wouldn’t say, have 1-1 dinner with in a non-professional context. (You don’t necessarily like this person but can at least tolerate them.) You’ll shoot these people a quick email w/out much thought

PRL6: Friend. Someone whose company you actively seek out. You would happily do this person a favor and usually feel comfortable asking for one. You have a low barrier to communication with them — shooting a quick text, etc.

PRL7: Good friend. A friend you prioritize above your other friends. These are the people you might invite to your wedding, talk about feelings with, and ask vulnerable questions.

PRL8: Good friend. A friend you prioritize above your other friends. These are the people you might invite to your wedding, talk about feelings with, and ask vulnerable questions.

PRL9: Family. Sometimes these people are chosen, not blood family. What makes someone family beyond blood is ineffable. Maybe it’s that these are the relationships that are too close to walk away from, no matter how much the other person pisses you off.

CORRECTION PRL 7: Friend. Someone whose company you actively seek out. You would happily do this person a favor and usually feel comfortable asking for one. You have a low barrier to communication with them — shooting a quick text, etc.