Hunger: the body's way of signaling that it is running short of food and needs to eat something. Hunger can lead to malnutrition.
Malnutrition: defined as a state in which the physical function of an individual is impaired to the point where he or she can no longer maintain natural bodily capacities such as growth, pregnancy, lactation, learning abilities, physical work and resisting and recovering from disease. The term covers a range of problems from being dangerously thin (see Underweight) or too short (see Stunting) for one's age to being deficient in vitamins and minerals or being too fat (obese).
Protein energy malnutrition: a form of malnutrition measured not by how much food is eaten but by physical measurements of the body - weight or height - and age (see Stunting, Wasting, Underweight).
Stunting: reflects shortness-for-age; an indicator of chronic malnutrition and calculated by comparing the height-for-age of a child with a reference population of well nourished and healthy children. According to the UN Standing Committee on Nutrition's 5th Report on the World Nutrition Situation (2005) almost one third of all children are stunted.
Undernourishment: describes the status of people whose food intake does not include enough calories (energy) to meet minimum physiological needs. The term is a measure of a country's ability to gain access to food and is normally derived from Food Balance Sheets prepared by the UN Food and Agriculture Organization (FAO).
Underweight: measured by comparing the weight-for-age of a child with a reference population of well nourished and healthy children. It is estimated that the deaths of 3.7 million children aged less than five are associated with the underweight status of the children themselves or their mothers (source: Comparative Quantification of Health Risks, 2004).
Wasting: reflects a recent and severe process that has led to substantial weight loss, usually associated with starvation and/or disease. Wasting is calculated by comparing weight-for-height of a child with a reference population of well nourished and healthy children. Often used to assess the severity of emergencies because it is strongly related to mortality.