Likelihood is how probable or expected something is to happen. When meteorologists say there's a high likelihood of rain tomorrow, they mean rain is very probable. When your teacher mentions the likelihood of a pop quiz, she's talking about how likely it is to occur.

The word helps us think about possibilities more precisely than just saying something “might” happen. A low likelihood means something probably won't occur, even though it's possible. A high likelihood means you should probably prepare for it. If you never study your spelling words, there's a strong likelihood you'll struggle on Friday's test.

Scientists and researchers use likelihood constantly. A doctor might discuss the likelihood of recovery from an illness. An engineer calculates the likelihood that a bridge design will hold its weight safely. Even in everyday conversation, we use it to weigh our options: “What's the likelihood we'll finish this project by Friday?”

The word is similar to probability but feels less mathematical and more conversational. You might discuss probability in math class but talk about likelihood at the dinner table when deciding whether to bring an umbrella tomorrow.