The difference between Thyristors and SCRs

The term silicon controlled rectifier (SCR) is sometimes used interchangeably with thyristors however, the former is a brand name introduced by General Electric to describe a particular kind of thyristor that it manufactured

There are various other types including diacs and triacs which are designed to work with alternating current so the terms are not completely synonymous. Whether it’s called thyristor or SCR we're referring to the same semiconductor device.