Malnutrition is not getting necessary nutrition to be healthy. It is considered a more scientific and official term than starvation which has negative associations. Malnutrition is not, however, simply a matter of eating too little. Someone can be malnourished if they eat an unhealthy diet.
Children whose daily diet contains less carbohydrate and protein do not grow well. They do not gain weight. Their hands and legs appear as skin and bones. They cry all the time with hunger. They are not active and have sunken eyes. Such children often fall sick. Lack of a particular vitamin is another kind of malnutrition which can cause a particular deficiency disease.