Colloquial language is used in informal writing situations and creates a conversational tone. Everyday spoken language gives your writing a casual, relaxed effect. Colloquial language is not necessarily “wrong,” but it is used when a writer is trying to achieve informality.
Why does authors use colloquial?
Writers primarily use colloquialism in literature to establish character and voice. Colloquial dialogue can signal a character's social background, level of education, and/or where they live. Colloquial language gives readers a lot of information without clunky exposition.
What is the effect of colloquial language in dialogue?
The successful use of colloquial speech in dialogue is a key element of character development. Done right, it can impart a strong sense of realism – of time, of place, of character – to your work. It can draw your readers into the story and help them relate to your characters.