What are GRE Subject Tests?

The GRE Subject Tests are similar to the SAT Subject Tests in that they test your knowledge of a particular subject like chemistry or literature. Not every school requires a GRE Subject Test, but many of the most competitive programs do. ETS offers the Subject Tests three times a year; they are not part of the standard GRE.  There are six GRE Subjects: biology, chemistry, English literature, math, physics, and psychology.