in Linux Device Driver3 and Understanding the Linux Kernel. Some buzzword appear many times without definition

process context: referenced in both books, but no definitions

interrupt context: Understanding the Linux Kernel gives definition

atomic context: only appear in LDD3 and without definition. "it specifies that the kernel is currently executing either an
interrupt handler or a deferrable function"

when reading tutorial, these three buzzword are referenced by many things. So I think the most important thing is to try figure out the exact definition, then I can understand those references.

I also did some search online, no very clear sources.Could any one gives good definition and the source of that definition? Thanks so much