In Portuguese, the most common ways to say hello are [Olá](javascript:void(0)) and [Oi](javascript:void(0)). [Olá](javascript:void(0)) is a slightly more formal greeting used across both European and Brazilian Portuguese, suitable for various situations including when you don’t know the person well. [Oi](javascript:void(0)) is more informal and casual, widely used in Brazil among friends and familiar people. Another informal greeting used mainly in Brazil is [E aí](javascript:void(0)), which can mean "Hey" or "What's up?" These greetings cover a range of contexts, from formal to very casual interactions. Other related greetings include [Bom dia](javascript:void(0)) for "Good morning," [Boa tarde](javascript:void(0)) for "Good afternoon," and [Boa noite](javascript:void(0)) for "Good evening" or "Good night".