Abstract length varies by discipline and publisher requirements. Typical length ranges from 100 to 500 words, but very rarely more than a page and occasionally just a few words. An abstract may or may not have the section title of "abstract" explicitly listed as an antecedent to content. Abstracts are typically sectioned logically as an overview of what appears in the paper, with any of the following subheadings: Background, Introduction, Objectives, Methods, Results, Conclusions. Abstracts in which these subheadings are explicitly given are often called structured abstracts. Abstracts that comprise one paragraph (no explicit subheadings) are often called unstructured abstracts.