You might see a gorilla in a zoo, but a guerrilla (sometimes spelled with one "r"), is someone who belongs to a group of independent fighters. If you remember your high school Spanish, you'll know the difference.

A gorilla is a type of large African ape. Sure they fight, but that's not why they're called gorillas. When they show up in the news, they're usually just monkeying around:

This short clip of a Silverback gorilla in Kent walking upright on his hind legs, like a human, has become an internet sensation. (BBC)

Anaklet says we're going to surprise some gorillas eating breakfast. (Time)

A guerrilla, on the other hand, is a fighter who's a part of a rebellious group that's battling a government or other authority, and likes to raid and ambush. The word has picked up a casual meaning of describing anything that's meant to take you by surprise. Here are some examples:

Al-Shabab had spoken of a switch to guerilla warfare, which could mean more suicide bombings as well as grenade attacks and land mines, he says. (BBC)

Guerrilla Marketing is a phrase coined by Jay Conrad Levinson as a take-no-prisoners way of marketing. (Guerrilla Marketing)

So how will knowing your high school Spanish help you keep them straight? Guerrilla comes from the Spanish word for a war made up of skirmishes. That guerilla is related to guerra for (you guessed it), war. If you remember that guerra is war and guerrilla is little war, you'll remember that in English, independent fighters are guerrillas, no matter how hairy they are.