1. A casual or colloquial way of expressing something, not following formal rules or conventions
The informal form of 'you are' is 'you're'
A forma informal de 'você está' é 'tá' ou 'tô'
2. A style of communication, dress, or behavior that is relaxed and not bound by strict rules
They decided to have an informal gathering instead of a formal dinner party
Eles decidiram ter um encontro em forma informal em vez de um jantar formal
3. In linguistics, a variant of language used in casual contexts rather than formal ones
The teacher explained the difference between formal and informal speech
A professora explicou a diferença entre a forma informal e formal de falar