“ps aux” works but “ps -aux” doesn't

Question

This might seem like a silly question but I haven\'t been able to find a clear answer.

This website states that the dash is optional in

ps aux
         


        

Answer 1

man ps

will give you this:

 The biggest change is in the interpretation of the -u option, which now
 displays processes belonging to the specified username(s).  Thus, "ps
 -aux" will fail (unless you want to know about user "x").  As a conve-
 nience, however, "ps aux" still works as it did in Tiger.