The word dry has several related meanings:

1. When something is dry, it lacks water or moisture. A towel fresh from the dryer is dry. A desert is dry because it gets very little rain. Your throat feels dry when you need a drink. When you dry the dishes after washing them, you're removing the water so they can be put away. Scientists call extremely dry conditions arid.
2. Dry can also describe a kind of humor that's clever but delivered in a deadpan way, without smiling or changing your voice. When someone makes a dry remark, they might say something funny while keeping a completely straight face, making you wonder for a second if they're joking.
3. In another sense, dry describes writing or speech that's boring and lacks interesting details. A textbook might be criticized for being too dry if it presents facts without any engaging stories or examples. A dry lecture puts students to sleep because the speaker drones on without energy or personality.