To detail something means to describe it thoroughly, including all the small parts and specific information. When a teacher asks you to detail your science experiment, she wants you to explain exactly what you did, step by step, covering every stage of the process. When a witness details what happened at an accident, they describe everything they saw, even the small things that might seem unimportant.

A detail (as a noun) is one of those small, specific parts. In a painting, the details might include the individual petals on a flower or the tiny wrinkles in someone's clothing. When you're reading a story, the details are the specific facts: not just “a dog,” but “a shaggy golden retriever with muddy paws and a torn ear.” Good writers use precise details to help readers picture exactly what's happening.

The word also means a small unit or group assigned a specific task, especially in the military. A detail might be sent to guard a building or clean equipment.

When someone says “don't sweat the details,” they mean don't worry too much about the small stuff. But those details can matter more than people think. The difference between a believable story and an unconvincing one often comes down to whether the writer included the right details.