.IR tgid .
(By contrast,
.BR kill (2)
-can only be used to send a signal to a process (i.e., thread group)
+can be used to send a signal only to a process (i.e., thread group)
as a whole, and the signal will be delivered to an arbitrary
thread within that process.)
.BR tkill ()
is an obsolete predecessor to
.BR tgkill ().
-It only allows the target thread ID to be specified,
+It allows only the target thread ID to be specified,
which may result in the wrong thread being signaled if a thread
terminates and its thread ID is recycled.
Avoid using this system call.