so long

interjection

Informal.

1. goodbye.

   I said so long and left.

so long

1. informal,  farewell; goodbye

adverb

1. slang,  for the time being; meanwhile

Word History and Origins

Origin of so long¹

An Americanism dating back to 1840–50

Idioms and Phrases

Good-bye, as in So long, we'll see you next week. The allusion here is puzzling; long presumably means “a long time” and perhaps the sense is “until we meet again after a long time,” but the usage has no such implication. [Colloquial; first half of 1800s]

Example Sentences

The fact that the effects lasted so long tells us even more.

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The downside: As I’ve aged, the list has become so long it’s hard to keep track.

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That is because the politicians who have backed themselves into this corner don’t seem to mind inflicting economic damage—so long as they escape blame.

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“We’ve been living in fear for so long, waiting for the next bomb to come, to lose another friend. But I also know the war isn’t over yet.”

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Afterward, Mr. McIlroy said he doesn’t mind a little chirping from the fans, so long as it comes between strokes.

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Related Words

• goodbye 
• send-off 
• sendoff