hierarchical file system
Computing term for a file system organized in a tree-like structure of directories and subdirectories.
UNIX-like operating systems use a hierarchical file system.
In a hierarchical file system, directories branch out from the root directory at the top.
Compound of 階層型 (hierarchical type) + ファイルシステム (file system). The term is a direct calque from English 'hierarchical file system'.