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.

The sunk-cost fallacy tempts people to pay escalating premiums because they’ve paid in for so long.

From MarketWatch • May 6, 2026

Maybe we should be surprised that, for so long, they did the work for free.

From Slate • May 3, 2026

They pay their stated rate of income so long as the underlying asset doesn’t fall more than a predetermined percentage by certain dates.

From The Wall Street Journal • May 1, 2026

Having lived in the area "for so long", she adds that it's "sad" to see the community feeling "slipping away".

From BBC • May 1, 2026

For the first time in so long, Danny hadn’t had trouble sleeping.

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