have a word with sb的意思是：和……说句话，请看下面的例句：.
I wonder if I can have a word with Lucy?
I think I’ll have a word with the boss in private.
have words with sb的意思是：与……吵嘴（争论），请看下面的例句：
I shall have words with these stupid classmates of mine!
I want to have words with those two boyss at the back of the class.