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A switch port running in half duplex is basically the same as any other two hosts running half duplex between them. When either host transmits, each has a chance to collide with a transmission from the other host.
As frames between switch ports are buffered, hosts on two different ports, even if they transmit at the same time, won't directly collide. Again, though, if port is running half duplex, host can collide with switch port retransmitting the other host's traffic. I.e. two hosts, on two different ports, behave (practically) as if they were directly connected. The advantage of a switch, however, is another two hosts transmitting to each other won't collide between the two pairs, as they would on a hub. I.e. on a hub A<>B frames may collide with C<>D frames, but they shouldn't on a switch.
If host ports are running in full duplex, there should be no collisions at all (which would also be true with a pair of hosts on a full duplex wire between them).
NB: above is just for unicast when switch "knows" destination MAC's port.
