$SOL "Sol" has multiple meanings. In music, it's the fifth note of a major scale. It's also the Spanish and Portuguese word for "sun." In astronomy, a "sol" is a Martian solar day. Chemically, a "sol" is a colloid with solid particles in a liquid. Historically, "Sol" was a Roman sun god and an old French coin. It can also be an abbreviation for "solution" or slang for "shit out of luck."