bridge
termA device that joins two network segments at layer 2, forwarding only the frames that need to cross.
The bridge is the switch's ancestor and the word survives where the switch's does not: spanning tree still elects a root bridge, and virtualisation still calls a software switch a bridge. The original purpose was to cut a collision domain in half while keeping one broadcast domain, which is exactly what a modern switch port does per port - the idea did not go away, it multiplied.
In the standards the bridge never went away. IEEE 802.1Q, whose active edition is 802.1Q-2022, specifies the operation of MAC Bridges and VLAN Bridges, and it has absorbed the old bridging standard, 802.1D, whose content now lives inside it. In the standard's vocabulary a switch is a bridge with many ports.
The word also survives in software. The Linux kernel's bridge is a device that 'connects two or more network segments and operates at the data link layer (Layer 2)' and forwards transparently, and it is what connects virtual machines and containers to a physical network. When a hypervisor diagram shows a bridge, read it as a switch that happens to live in the kernel.
Spanning tree still elects a root bridge, and every switch in it carries a bridge ID made of a priority and a MAC address, which keeps the oldest name in the family on every Layer 2 engineer's screen.
Also known as: bridging