Colloquial describes the casual, everyday language people use when talking with friends and family, rather than the formal language they might use in school essays or official speeches. When you say “gonna” instead of “going to,” or “kids” instead of “children,” you're using colloquial language.

A colloquial expression is a phrase that sounds natural in conversation but might seem too informal for a book report. Saying “my bad” when you make a mistake is colloquial, while writing “I apologize for my error” is formal. Telling your friend “that test was a piece of cake” uses colloquial language, while telling your principal “the examination was quite manageable” does not.

Different regions often have their own colloquial words. In some places, people say “pop” for a fizzy drink, while others say “soda” or “coke.” These regional differences make language interesting and show how people naturally shape the words they use.

Writers sometimes include colloquial dialogue to make their characters sound authentic and real. When you read a story where characters talk like actual people you know, rather than like narrators in a documentary, that's colloquial language at work. It helps readers feel like they're listening to a real conversation.