"On nie jest moim przyjacielem, on jest moim znajomym."

Translation: He is not my friend, he is my acquaintance.

[RadhaTereska]

since the Polish uses "moim" in the second part, I would say my acquaintance and not "an" acquaintance

[PierreMDL]

Acquaintancezoned

[PolishBagel]

Judging by the "znajo" in "znajomym" I'm assuming that it just refers to someone you know, or have met. Is this correct? Does "znajomym" exclude friends?

[Jellei]

"znajomy" is "someone I know". Friends are included, but... they are just closer, right? They are more than "znajomi".

"znajomi" is the word for "friends" on Facebook, which itself tells a lot. Usually the list of people I know, but not necessarily know well.

[PolishBagel]

Dzięki za odpowiedż!

[MaxMatr]

In any case not "an friend"

[BruceAdams14]

Why do we get really hard spellings in practices that we don't have to spell yet in the 'real' lessons?

[Elkah1]

Why would it not be moj, moja, or moje? Why now moim?

[alik1989]

This is a "X jest Y" type of sentence where the subject complement Y must take the instrumental case.

https://forum.duolingo.com/comment/16373167

Possessive pronouns take the same case as the noun they refer to, so since przyjaciel and znajomy take the instrumental case, so should mój.

https://en.wiktionary.org/wiki/m%C3%B3j#Declension_2