Pendentives and Squinches

I have always had a hard time explaining the difference between a squinch and a pendentive to my students, in part because I have never had good pictures of either.
Well, I just got back from EGYPT and among the hundreds of pictures I took were some mosque ceilings.
This upper one is a squinch,
from the 12th century Al-Hussein mosque in Islamic Cairo:

And this detail shows a dome supported on pendentives,
from the dome of the Muhummad Ali Mosque in Cairo's citadel,
built in the 19th century:

Here are some fancy 14th century pendentives from the An Nassir Mohammed Mosque in the Citadel of Salah-AdDin (Saladin) at Cairo:

Pendentives curve out,
squinches curve in.
I think this will help teach that point more effectively.
I will have many, many more posts to come!