Formal:
* শুভ রাত্রি (Shubho Ratri) - This is the most formal way to say goodnight.
* সুস্বাস্থ্যে থাকুন (Suswasthye Thakun) - This means "Stay healthy" and is a polite way to end a conversation before going to bed.
Informal:
* শুভ রাত্রি (Shubho Ratri) - This is also used informally.
* ভালো রাত্রি (Bhalo Ratri) - This means "Good night" and is a more casual way to say goodnight.
* স্বপ্ন দেখো (Swapna Dekho) - This means "Dream well" and is a friendly way to say goodnight to someone you know well.
* আপনার ভালো রাত্রি হোক (Aponar Bhalo Ratri Hok) - This means "Have a good night" and is a polite way to say goodnight.
To someone younger or someone you're close to:
* ভালো রাত্রি (Bhalo Ratri)
* স্বপ্ন দেখো (Swapna Dekho)
The best way to choose which phrase to use depends on the situation and your relationship with the person you are talking to.