What is hunger?

What really is hunger?  According ro the Oxford Englsih Dictionary, hunger has three meanings.
1. The uneasy painful sensation caused by want of food; craving apetite.  Also the exhausted condition caused by want of food.
2.The want or scarcity of food in a country.
3. A strong desire or craving.
So, according to this, each one of us has experienced hunger.  Malnutrition, however, is a better definition of world hunger.  Malnutrition is a very general term that indicates a lack of the appropriate sustinence a person needs.