informal
adj.adj. relaxed and friendly rather than serious or official. You use this to describe clothes, language, or events where you do not need to follow strict rules.
adj. denoting a style of writing, speaking, or behaviour that is relaxed, casual, and suited to everyday social interactions. Frequently contrasted with 'formal' in linguistic and social contexts.
The party is informal, so you can wear jeans.
We had an informal meeting over coffee to discuss our ideas before the official presentation next week.
While the written report required a professional tone, the team maintained an informal atmosphere during their brainstorming sessions to encourage a free exchange of creative concepts.
From in- + formal.
Typically placed before the noun it modifies or after a linking verb like 'be'.