Already Not Yet

There is a word which fascinates me very much.  It only has three letters. And depending on which way it is used can mean opposite things.  When a person says it sometimes I have to think twice so as to decipher which meaning they are using:

      Yet. 

      Are you at the store yet?

This could be heard two ways (at least I think only two!).  The first--you are driving down the road in your car.  Your mom calls you on your cell phone.  She says "are you at the store yet?"  Meaning, have you arrived at the store?  The second--you are busy putting 20 cans of black olives in your shopping cart because they are on sale for 89 cents, and you love black olives.  Your cell phone rings.  It's your mom.  You think to yourself, oh, perhaps she needs me to pick up something else at the store!  Mom says "are you at the store yet?"  Meaning, are you at the store still?  Is it just me, or isn't that fascinating!?