An amount of storage capacity presented to a host to format with its own file system is:

A LUN (Logical Unit Number) is a logical identifier used to address block-level storage devices in a SAN, not the general term for storage capacity presented to a host for formatting.

A zone is a SAN fabric configuration construct that controls which hosts can communicate with which storage targets - it is an access control mechanism, not a unit of storage capacity.

A share is a defined allocation of storage capacity that is handed off to a host, giving that host the ability to format and manage it with its own chosen file system. This is the standard term used in storage networking to describe capacity presented to clients or hosts for their own use and file system application.

An export is an NFS-specific term for a directory on a server made accessible to NFS clients and refers to file-level access to already-formatted storage, not raw capacity for host formatting.