Formal:
* Добро пожаловать (Dobro pozhalovat') - This is the most common and formal way to say "welcome" in Russian. It literally translates to "Welcome (with good wishes)".
Informal:
* Добро пожаловать! (Dobro pozhalovat!) - This is a shortened version of the formal greeting, still quite common in everyday situations.
* Рад (а) тебя (вас) видеть! (Rad (a) tebya (vas) videt!) - This means "Glad to see you!". This is a more personal and friendly way to say "welcome".
* Привет! (Privet!) - This means "hello" and can also be used as a casual "welcome" in informal settings.
In addition to these, you can also use phrases like:
* Приятно познакомиться! (Priyatno poznakomitsya!) - This means "Nice to meet you!".
* Заходите! (Zahodite!) - This means "Come in!".
The best way to choose the right "welcome" in Russian is to consider the context and the level of formality of the situation.