Hi Jmason. They both mean ''only'' and can be used interchangeably. Sólo quiero saber la diferencia Solamente quiero saber la diferencia. "I just want to know the difference" Sólo me queda uno/ Solamente me queda uno (Theres only one left). Here's something I was reading the other day: apparently the RAE (spanish language regulators) have decided that sólo no longer needs the written accent, unless it is needed for disambiguation. (to avoid confusion with adjective "solo" = alone)

Hi, I think "solo" is adjective and "solamente" is adverb. You can say: Estoy solo - I'm alone, but you can't say Estoy solamente. Then when it means only you can use both, I think: Te quiero solamente/solo a ti - You are my only love. And that's all what I know.

They are synonims and interchangeable with each other when they are used as an adverb; when used as an adjective or a noun the correct word is "solo".