familiar because it means friend
Colloquial refers to the level language is used in everyday speech. This presents a neutral tone, not so much informal or formal. This is the level used in ordinary conversation. Familiar is a level of language that reflects the close relationship of the people speaking. The intimacy is observed in the use of details and personal references in speech.
Make a mess of something, make a mistake.
c'est ennuyeux c'est rasoir / c'est barbant / c'est la barbe (familiar / colloquial)
Colloquial language refers to informal language commonly used in casual conversations among friends or in everyday situations. Familiar language, on the other hand, refers to language that is intimate and personal, often used between close individuals like family members or romantic partners.
You can use colloquial language when you speak to a person who you know well, and you are comfortable to speak to someone. You should not use colloquial language with someone who you do not know.
quotidian, recurring, customary, simple, vulgar, vernacular, usual, frequent, idiomatic, colloquial, conversational, informal, familiar, common
Unless her name is Eve or Hannah, you might want to stick with Sis.
Informal language is casual, conversational, and often includes slang or colloquial expressions. It is used in familiar settings where a relaxed tone is appropriate.
The French word "gosse" is a colloquial term that is used to refer to children or kids. It is a casual and familiar way to describe young individuals.
In his book 1984, when George Orwell wrote "Big brother" is an example, because he used it specifically to describe his world. Using a word that had never been used in such a way.
Sis
"Kakashka" is a colloquial Russian term that means "poop" or "feces." It is a familiar or childish way of referring to excrement.