A host is any hardware device that has the capability of permitting access to a network via a user interface, specialized software, network address, protocol stack, or any other means. Some examples include, but are not limited to, computers, personal electronic devices, thin clients, and multi-functional devices.
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Almost any kind of computer, including a centralized mainframe that is a host to its terminals, a server that is host to its clients, or a desktop personal computer (PC) that is host to its peripherals. In network architectures, a client station (user’s machine) is also considered a host because it is a source of information to the network, in contrast to a device, such as a router or switch, that directs traffic.
NIST SP 800-44 Version 2 under Host