extention

Extention is not a widely recognized term in standard reference works. It is most often a misspelling of the word extension, and when seen in writing it is frequently the result of a typographical error. In rare cases, Extention may be used as a proper noun, brand name, or project title, but it does not have a single established definition in the way that extension does.

When a term is meant in common usage, extension can refer to several concepts across different domains. In computing, a file extension is the suffix added to a filename after the final dot, such as .txt or .jpg, which helps identify the file type. A software extension or browser extension is an add-on that enhances a program’s or browser’s functionality. In architecture and construction, an extension is an addition to a building that increases its usable space. In mathematics, a field or ring extension describes a larger algebraic structure that contains a given one as a substructure. In telecommunications, an extension can denote an internal telephone line connected to a larger system.

For formal writing, it is advisable to use the standard spelling “extension.” If you encounter “Extention,” consider whether it is a typographical error or a stylized name, and verify the intended meaning from context. See also extension for related disambiguation.