An outline is an organized plan that shows the main points and supporting details of something you're going to create, like an essay, speech, or project. Think of it as a skeleton or blueprint: before building a house, an architect draws plans showing where each room goes. Before writing a report, you create an outline showing what each paragraph will cover.

A typical outline uses numbers and letters to show how ideas connect. The big ideas (marked with Roman numerals like I, II, III) come first, then smaller supporting points branch off underneath them (marked with letters and numbers). If you're writing about dinosaurs, your outline might look like: “I. Herbivores” with “A. Triceratops” and “B. Brachiosaurus” listed below, then “II. Carnivores” with different examples underneath.

Creating an outline before you write helps you organize your thoughts and spot problems early. You might realize you have too much information about one topic and not enough about another. You can rearrange sections easily in an outline, while moving whole paragraphs around in a finished essay is much harder.

The word also describes the outer edge or boundary line of something. You might draw the outline of your hand by tracing around it, or see the outline of mountains against the sunset sky. When something is outlined against the light, you see its shape but not its details.

As a verb, outline means to describe the main parts of something without going into every detail. You might outline your plan for a science fair project before you start building it.