What is the reverse transfer capacitance of a JFET?

[Jasper Chow]

I looked it up in a terminology dictionary issued by JEDEC. It specifies the capacitance as follows:

short-circuit reverse transfer capacitance, common source (Crss): The capacitance between
the drain and gate terminals with the source connected to the guard terminal of a three-terminal
bridge

What does "the guard terminal of a three-terminal bridge" mean?

 

[FvM]

In the schematic shown below, the ground terminal would act as guard

Generally, you'll use a setup where Cds and Cgs don't affect the Cdg (Crss) measurement.

 

[Jasper Chow]

In the schematic shown below, the ground terminal would act as guard

Generally, you'll use a setup where Cds and Cgs don't affect the Cdg (Crss) measurement.

Thanks. But I am still confused with the "three terminal bridge" and "guard terminal". I wonder whether the "guard" is a misphrased word for 'ground'?