Be careful. Rajiv provides anexcellent definition of a collision, but not necessarily a collisiondomain.
A collision domain is where acollision might occur. If we configure both devices in a point-to-pointmanner and use full duplex, notice a collision will not occur, but we stillconsider this a collision domain.
So, for example, we have aCisco switch with 10 workstations connected to it, we have 10 collisiondomains.