What is the difference between an SCR and a TRIAC?

A thyristor is another name for an SCR, which stands for Silicon Controlled Rectifier.

Thyristors or SCRs are bi-directional devices used to control the flow of AC current. Once triggered, the device remains "on" until the next wave of current crosses zero after the trigger is removed.

For more information about thyristors or SCRs see the Related link shown below.