Past Perfect:

Occasion: sth happened before sth else.

1 2

past Now

Auxiliary: (+)had (-)hadn’t

Main structure: I had (already) done sth.

I had done sth before I did sth.

After I had done sth,I did sth.

That/it was the first time that I had done sth.

The first time I did sth was 3 months ago. Before then, I had never done sth.

Conditional statements:

Type 3: (past)(unreal)

If I had done sth , I would have done sth.

Had I done sth

Mixed 2,3: (past, now)(unreal)

If I had done sth, I would do sth.

Passive: I had done sth. Sth had been done.