pthread functions “_np” suffix

Question

What does \"_np\" suffix mean here:

pthread_mutex_timedlock_np

or in macros

PTHREAD_MUTEX_TIMED_NP

Upd:

Answer 1

Non standard extensions -- i.e., Non Portable. ref (from the Internet Archive)

Answer 2

It stands for Non Portable.

That is, it's platform specific extensions to the standard pthreads functions.