I was asked why we use "a" when saying, for example, "That person has a nice smile" instead of "That person has nice smile."
I looked up the rules for using the indefinite article "a" and thought the rule of using it to introduce new people or things might apply (but using "the" afterwards wouldn't apply in this case).
What's your opinion?
***** A NON-TEACHER'S COMMENT *****
Tom: Sue always has such a nice smile on her face.
Martha: Yes, she does.
Ralph: Believe me, the/that smile that you see on her face means
nothing. She is really a very angry and unhappy person.
Her smile is just an act.