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

“As the name suggests, a revocable living trust can be altered or revoked by the grantor at any time during their lifetime if their circumstances change, so long as they’re mentally competent.”

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"We said the location of the nitrogen-fixing bacteria is not important, so long as the fixed nitrogen can reach the plant, and the plant can use it."

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They travel across the country next weekend to play at Carolina, a team that won four of five not so long ago, including an upset of Green Bay.

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Occasionally, he said, the laughter went on so long it had to be edited out of episodes.

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“After? It takes so long to get these appointments. It can be three months before you see the specialists you’re supposed to see.”

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Related Words

• goodbye 
• send-off 
• sendoff