Formal:
* আবার স্বাগতম (abar swagatam) - This is the most formal way to say "welcome back".
* ফিরে আসার জন্য স্বাগতম (fire asar jonno swagatam) - This translates to "welcome back for coming back".
Informal:
* ফিরে এসেছ? স্বাগতম! (fire eseche? Swagatam!) - This translates to "Did you come back? Welcome!" and is a very friendly way to greet someone.
* আবার দেখা হচ্ছে! (abar dekha hochche!) - This translates to "Seeing you again!" and is a casual way to say "welcome back".
Other options:
* তুমি ফিরে এসেছ! (tumi fire eseche!) - This translates to "You came back!" and is a neutral way to express someone's return.
You can choose the best option based on the context and your relationship with the person.