Least means the smallest amount, the lowest degree, or the minimum of something. If you have the least money in your pocket among your friends, you have less than anyone else. If something costs the least, it's the cheapest option. When your teacher assigns the problem that takes the least time to solve, she's choosing the quickest one.

The word often appears in comparisons. You might say, “Of all my subjects, math requires the least effort for me,” meaning it's easier than your other classes. Or someone might choose “the path of least resistance,” taking the easiest route available.

Least is the opposite of most. While most points to the maximum or greatest amount, least points to the minimum. When you say “I'm the least worried person here,” you're claiming to be the calmest one around.

People also use least in phrases like “at least,” which means “at a minimum” or “anyway.” If you say, “I didn't win, but at least I tried my best,” you're finding something positive even in disappointment. And “not in the least” means “not at all”: “I'm not tired in the least” means you have plenty of energy left.