thematicBreak

ThematicBreak is a term used in Markdown and related parsing tools to denote a horizontal rule, a visual divider that marks a thematic break in content. In many tooling ecosystems it is represented as a node type or token called thematicBreak, or simply as a horizontal rule, within the document’s abstract syntax tree.

Syntax for a thematic break in most Markdown flavors requires a line containing three or more of the same character—hyphen (-), asterisk (*), or underscore (_)—with optional spaces between characters. The line must not contain other content and is typically accepted when it appears on its own line, possibly with surrounding blank lines. The characters may be repeated in any of the accepted styles, such as ---, ***, or ____, with spaces like - - - also allowed in some implementations.

Rendering and purpose: When parsed, a thematic break is rendered as an HTML horizontal rule, typically the <hr> element. Its purpose is to visually separate sections or topics within a document, signaling a shift in content rather than merely decorating the page. It should be used to indicate a real division in thought or structure.

Beyond rendering, the thematicBreak node type is used in the abstract syntax trees of Markdown processing ecosystems (for example, remark, unified, and related tooling) to facilitate analysis, transformation, or styling of document structure. These trees enable applications to manipulate horizontal rules as distinct structural elements.

Accessibility considerations: An HR should convey a meaningful division; when used, authors may provide existing headings or descriptive context around the break. Avoid relying on decorative horizontal rules without semantic purpose, as they may be ignored by assistive technologies.