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

And somehow, a threat like that could make a cop’s behavior more legal and not less, so long as it’s characterized as a “warning.”

From Slate • Apr. 21, 2026

"I don't think I imagined at all the tournament would be in Sheffield for so long."

From BBC • Apr. 20, 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

It had been so long since he’d met someone he shared something in common with.

From "The Way to Rio Luna" by Zoraida Cordova

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