To say goodbye, the expression varies depending on the language and context. For example:

• In English, simply say "Goodbye" or "Bye."
• In Italian, a formal goodbye is "Arrivederci," while "Ciao" can be used casually both for hello and goodbye.
• In French, use "Au revoir" for goodbye and "Salut" informally.
• In Spanish, common goodbyes are "Adiós" or "Hasta luego" (see you later).
• In Mandarin Chinese, "再见 (Zài jiàn)" is the usual way.
• In Arabic, "مع السلامة (Ma’a salama)" means goodbye with a wish of peace.
• In Dutch, "Tot ziens" means "until I see you again," and "Doei" is casual bye.

These are just a few examples, and many languages have formal and informal ways to say goodbye or variations depending on the social context. Let me know if a specific language or a certain type of goodbye is desired for a more tailored answer.