Formal:
* Bem-vindo(a): This is the most common and formal way to say "welcome" in Portuguese. You can use it for both singular and plural, but you need to adjust the ending to match the gender of the person you are welcoming.
* Bem-vindo: Welcome (masculine)
* Bem-vinda: Welcome (feminine)
* Bem-vindos: Welcome (masculine plural)
* Bem-vindas: Welcome (feminine plural)
Informal:
* Seja bem-vindo(a): This is a more friendly and casual way to say "welcome" in Portuguese. The same gender rules apply as above.
* Bem-vindo/a à [lugar]: This is a more specific way to say "welcome to [place]" and it is appropriate for both formal and informal contexts.
Other options:
* Boas-vindas: This is a literal translation of "welcome" and is often used in more formal settings.
* Bem-vindo(a) de volta: This means "welcome back" and is used to greet someone who has returned.
The best option for you will depend on the specific situation and your relationship with the person you are greeting.