so long

interjection

, Informal.

1. goodbye:

   I said so long and left.

so long

sentence substitute

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 pipeline from bench to bedside is decades-long and often things that work in animals fail when they get to clinical trials. Is it taking so long because sex isn't being considered enough?" said Rowe.

From Science Daily

That means that everything that sabotaged us this time and has held us back for so long, we can fix.

From Salon

In the days that followed, the IRA issued a statement apologising for the grief it had caused the families of the Disappeared and that their suffering had continued for so long.

From BBC

Kyiv has been asking to use long-range Western missiles inside Russia for so long that Moscow has already taken precautions.

From BBC

They’ve been waiting so long for the first and perhaps only time to be teammates this season.

From Los Angeles Times

Related Words

• goodbye
• send-off
• sendoff