blues

noun

• 1 [treated as singular] (or plural often the blues) melancholic music of black American folk origin, typically in a twelve-bar sequence. It developed in the rural southern US toward the end of the 19th century, finding a wider audience in the 1940s as blacks migrated to the cities. This urban blues gave rise to rhythm and blues and rock and roll.
• [treated as singular] a piece of blues music:we’ll do a blues in C

• 2 (the blues) informal feelings of melancholy, sadness, or depression:she’s got the blues