Outlines can be informal or formal. Writers often complete informal outlines to help structure their work. Formal outlines are usually completed in preparation for official writing assignments. There are two types of formal outlines: Topic outlines and sentence outlines.
A topic outline is the most frequently used type of formal outline. In this format, each line is a word or phrase that represents a complete thought that will be included in the paper itself. Each word or phrase must clearly summarize the content for that section of the paper or essay. Roman numerals, capital letters, Arabic numerals and lowercase letters are used to organize the ideas by importance and logical sequence. Topic outlines are often used with papers that would be too lengthy for sentence outlines.
A sentence outline is a formal outline with complete sentences, rather than single words or short phrases. The headings of each section may or may not be stated as complete sentences, but everything else is stated completely. Sentence outlines are useful when completing persuasive writing, where one must state a thorough and compelling argument within an essay or speech. In this type of outline, each sentence must be in the same tense: Present, past or future. Each heading should be stated as a single sentence, rather than several. Each sentence in the outline must be a statement, not a question.
While both a topic outline and a sentence outline begin with a thesis statement, the individual statements in a sentence outline might be viewed as mini-thesis statements about each subtopic. These statements provide the specific words the author wishes to use in each section of the paper. In a sentence outline, each subsection ends with a period, since it is a complete statement. The words and phrases that make up the subsections of a topic outline do not require periods at the end.