A folding knife, typically a pocketknife.
An organizer that papers are kept in, usually with an index tab, to be stored as a single unit in a filing cabinet.
A virtual container in a computer's file system, in which files and other folders may be stored. The files and subfolders in a folder are usually related.
A machine or person that folds things.
A knife with blades or tools that the user can fold or retract into its handle, and of a size small enough for carrying safely and handily in a pocket, especially when suited to heavier duty uses or ad hoc applications outdoors or in workshops.