Remember when your brain exploded after your fourth grade math teacher told you “every square is a rectangle, but not every rectangle is a square!” Understanding the difference between an orchestra, a symphony, and a philharmonic is kind of like that. Every symphony is an orchestra, but not every orchestra is a symphony. Likewise, every philharmonic is a symphony, but not every symphony is a philharmonic.

Okay, let’s take a breath.

Orchestra is a broad term for any ensemble featuring a hefty lineup of strings. Two basic orchestras exist—chamber orchestras (small!) and symphony orchestras (big!). Chamber orchestras employ about 50 or fewer musicians (who may all play strings). As the name suggests, they play “chamber music”—older tunes written for private halls, aristocratic parlors, and glitzy palace chambers. Of course, contemporary composers still crank out chamber music, but the style peaked during the 17th and 18th centuries as wigged songsters like Haydn, Mozart, and Vivaldi tore up the scene.

On the flip side, a symphony orchestra can boast more than 100 players, who are divided into strings, woodwinds, brass, and percussion. As that name suggests, they play “symphonies”— hulking pieces that usually require 18 to 25 different instruments. (Think of the heavy hitters of the 1800s: Beethoven, Brahms, Wagner, and company.)

Essentially, if an orchestra is big enough to play a symphony, it’s a symphony orchestra. Simple!

Okay, maybe not.

A symphony orchestra and a philharmonic are the same thing—sort of. They’re the same size and they play the same kind of music. The two terms exist to help us tell different ensembles apart, especially in cities that boast multiple groups. For example: New York City is home to both the Brooklyn Philharmonic and the Brooklyn Symphony. They’re the same kind of orchestra, but they have different names so you don’t confuse them. The divide between symphony-philharmonic is just a matter of identity.

And that’s what makes them different. “Symphony orchestra” is a generic term, whereas “philharmonic orchestra” is always part of a proper name. So, you can call every philharmonic a symphony, but you can’t call every symphony a philharmonic—even though they’re the same.

And as for “pops?” That just means the orchestra isn’t afraid to let its hair down and play a jaunty show tune.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.