さようなら vs じゃあね

When to use it

さようなら is formal and slightly final: children to the teacher at the end of class, a farewell to someone you may not meet again, the end of a relationship. Written さようなら (long よう); さよなら in songs and casual writing. From 左様なら, ‘if that is so’.

Daily partings use something else. Friends: じゃあね, じゃ、また, またね, また明日, また来週, バイバイ. Colleagues: お疲れ様でした. To superiors: 失礼します / お先に失礼します. Leaving home: いってきます. Night: おやすみなさい. There is no register-neutral daily goodbye; you choose by relationship every time.

Examples

• じゃあね、また明日。（じゃあ ね、また あした）— See you, till tomorrow.
• 先生、さようなら。（せんせい、さようなら）— Goodbye, teacher. (school)
• お先に失礼します。— お疲れ様でした。（おさき に しつれい します。— おつかれさま でした）— I’m off. — Good work today. (office)

Traps for Spanish, English and French speakers

• Textbooks equate さようなら with ‘adiós / goodbye / au revoir’, so learners say it to colleagues at six o’clock. To a coworker it sounds like your last day; to a partner, like a break-up. The office goodbye is お疲れ様でした or お先に失礼します.
• ‘Hasta mañana’ and ‘à demain’ are not さようなら either: they are また明日. Spanish speakers have the right instinct, since in much of the Spanish-speaking world ‘adiós’ has drifted toward the same finality and ‘hasta luego’ is the everyday word. Map hasta luego → じゃあね / またね, adiós for good → さようなら.
• じゃあね is for equals and friends; to a teacher or boss it is too familiar. French ‘à plus’ has the same restriction, but ‘au revoir’ does not, and there is no Japanese ‘au revoir’ that works for everyone.
• Spelling: さようなら. Learners write さよなら in formal messages; keep the う there.