A subdirectory is part of a hierarchical file system. It represents a directory that is part of another directory, whether it was created or otherwise moved to be there. A subdirectory can contain files and other subdirectories – in theory, an indefinite chain of subdirectories in parent directories can exist on most devices, but in practice, it’s usually limited to nine. The main limitation is disk space – wherever the subdirectory is located, space is consumed by each of them, and eventually, that space runs out.
