subdirectory

A subdirectory is a directory that resides inside another directory. It is part of a hierarchical file system and is often referred to as a child directory, with its containing directory being the parent. Subdirectories can themselves contain more subdirectories, forming a tree structure.

Paths identify subdirectories. An absolute path begins at the root of the file system, for example /home/alice/projects or C:\Users\Alice\Documents. A relative path starts from a reference directory, such as projects or Documents\Reports, depending on the current location. Path separators differ by platform: forward slash on Unix-like systems and backslash on Windows.

In web hosting, a subdirectory of the site root corresponds to a nested folder on the server and is accessible via a URL that mirrors the path, such as https://example.com/blog/.

Creation and management. Subdirectories are created and deleted with system commands such as mkdir (and its variants) on most operating systems; rmdir or rm -r can remove directories, sometimes with a prompt for non-empty directories. Access is controlled by permissions or access control lists, which apply to the subdirectory and its contents. Deleting a subdirectory that contains files typically requires removing those files first or using recursive deletion.

Notes. The term subdirectory is widely used; subfolder is common in graphical interfaces. When writing software across platforms, prefer using platform-agnostic path handling to avoid issues with separators. Subdirectories enable organized data storage and modular website structure.