so long

American

interjection

Informal.

goodbye.

I said so long and left.

so long British

informal farewell; goodbye

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

adverb

slang for the time being; meanwhile

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

so long Idioms

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]

Etymology

Origin of so long

An Americanism dating back to 1840–50

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Rising oil prices are putting wind in the sails of oil and gas companies — but only for so long.

From MarketWatch • Apr. 23, 2026

Some have been in the U.S. so long that the countries they came from no longer exist.

From Los Angeles Times • Apr. 19, 2026

Ahmad agreed to sign, so long as he was allowed to write down everything that had been done to him in Chicago and London.

From Slate • Apr. 19, 2026

But it was hard for a party in power for so long, to present itself to the voters as the party of change, one source told the BBC.

From BBC • Apr. 17, 2026

He wasn’t sure if Aunt Hila believed him, but there was only so long she could stand there, clutching him like she was afraid of him escaping from between her fingers.

From "Night Owls" by A.R. Vishny

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023