A decimal outline is a structured way to organize information using a numbering system based on decimals. Each level of the outline is represented by a number, where the first digit indicates the main topic, and subsequent digits represent subtopics. For example, 1.0 could represent the main idea, while 1.1 and 1.2 would represent related subpoints. This method helps in clearly displaying the hierarchy of ideas and makes it easier to understand the relationships between different sections. Decimal outlines are commonly used in academic writing, presentations, and project planning to ensure clarity and organization.