Neither answer is correct. The glass is completely full--half full of water and half full or air. depends, if the glass was empty and you filled it half way, its half full, if it was full and you drank, threw out, ect. half the water its half empty
We drove to four different hotels before finding one that wasn't full. She couldn't eat dessert because her stomach was full. I won't feel good until my debts are paid in full. A pessimist sees the glass as half empty while the optimist views it as half full.
The glass is actually full. Full of half air and half water. As for the water content, technically, there is no difference, except as it pertains to the process of filling or emptying, i.e. if it was filled and you drank some, it is half-empty; if it was empty and being filled, it is half-full.