Formal:
* שלאָף גוט (shlof gut): This is the most common and polite way to say "sleep well" or "good night".
* גיי שוין שלאָפן (gey shoyn shlofn): This translates literally to "go already sleep". It's slightly less formal than "shlof gut", but still respectful.
Informal:
* שלאָף (shlof): This is the simplest way to say "sleep". It's often used between friends or family members.
* גיי שלאָפן (gey shlofn): This translates literally to "go sleep". It's more informal than "shlof" and often used with children.
You can also use phrases like:
* מאַך אַ גוטע נאַכט (makh a gute nacht): This translates to "have a good night".
* גיי שוין אריין אין בעט (gey shoyn arayn in bet): This translates to "go already into bed".
The best way to choose the right phrase depends on the specific situation.