terminology, @acronym{POSIX} defines the behavior of @command{nice} in
terms of a @dfn{nice value}, which is the nonnegative difference
between a niceness and the minimum niceness. Though @command{nice}
-conforms to @command{POSIX}, its documentation and diagnostics use the
+conforms to @acronym{POSIX}, its documentation and diagnostics use the
term ``niceness'' for compatibility with historical practice.
@var{command} must not be a special built-in utility (@pxref{Special