Intelligence is your ability to comprehend something, like calculus or why plants grow toward the sun.
Intelligence comes from the Latin word intelligere, "to understand," which makes sense because it refers to someone's ability to understand things. Your intelligence helps you pass math class and learn French. It means smarts — what you need at least some of to get through school. Intelligence has an exciting double life: it also refers to what spies are trying to get — information from the enemy. You can be born with it, or acquire it, especially if you're in the CIA.