Lucid means clear and easy to understand. When a teacher gives a lucid explanation of fractions, students immediately grasp how they work. A lucid piece of writing makes complex ideas simple, like when a science book explains photosynthesis so clearly that you can picture exactly what's happening inside a leaf.

When someone speaks lucidly about a complicated topic like how computers work or why the sky is blue, they cut through confusion and make everything make sense.

Lucid also describes clear thinking itself. After a good night's sleep, you might wake up with a lucid mind, ready to tackle difficult problems. During a lucid moment, someone who's been confused or sick suddenly thinks clearly again.

The opposite of lucid might be muddled, confusing, or unclear. If you've ever read instructions that left you more confused than when you started, you know what it's like when something isn't lucid. When you write or explain something, being lucid means your audience won't have to reread or ask what you meant. They'll understand the first time.