How is process and thread the same in Linux?

Question

I read that process and thread are the same thing on Linux, for example, this question says:

There is no difference between a thread and a process on Linux.

But I don’t understand how process and flow mean the same thing. I mean, a thread is what the processor does, and a process is just a wrapper for threads that allows threads to share memory. This image shows the relationship between the process and its threads:

Thus, process and flow do not mean the same thing!

Answer 1

Linux (POSIX) , , (filedescriptors, signal actions,...) "".

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google LinuxThreads NPTL, .