inode

This term is a technical portmanteau of index node, used almost exclusively within the context of computer science and operating system administration. It refers to the internal bookkeeping mechanism of a filesystem rather than the user-facing file itself. Because an inode stores metadata, a filesystem can run out of inodes even if there is still physical disk space available, leading to a specific type of system error where no new files can be created.

In professional technical documentation, the term is treated as a standard countable noun. It is rarely used outside of discussions regarding Unix, Linux, or similar filesystem architectures, and would be considered jargon in a general business or casual conversation.