Outlines' subcategories Subcategories, for example, give support for the important ideas expressed before. Along similar lines, a writer should examine how to develop an outline to divide the key themes into pertinent subtopics. Furthermore, each subcategory should provide appropriate supporting details. For example, the category of colors could be subdivided into red, blue, and green to reflect different aspects of color symbolism. Subcategories can also be used to organize material by type of document or process. A category for letters might include email messages, faxes, and handwritten notes. These could be divided further into subcategories such as personal vs business, with specific words added to indicate their content (e.g., "personal" emails). Categories for reports may include executive summaries, mission statements, and strategic plans; these could be broken down into more detail including audience profiles, job descriptions, and organizational charts. The use of categories and subcategories is very common in writing guides and manuals. Such documents may cover topics like formatting rules for manuscripts or guidelines on how to write effective abstracts for research papers. They often contain several subsections or sections under different headings, which assist readers in finding what they need quickly without having to read through everything in one go. Categories and subcategories can also help writers organize their thoughts when drafting a paper or speech.