Collision domain

The collision domain applies particularly in wireless networks, but also affected early versions of Ethernet.

So, that node could start sending as well, without a clue to the transmission already taking place and destroying the first packet.

[1] Early Ethernet variants (10BASE5, 10BASE2) were based on a shared wire and inherently half-duplex, representing a single, potentially large collision domain.

For Gigabit Ethernet and faster, no hubs or repeaters exist and all devices require full-duplex links.

In addition to the requirements of a shared wire medium, wireless networks add the hidden node problem where two senders can't hear each other's transmissions, but they cause a collision at the receiver between them.