Define the terms given below :

1. Health
2. Disease
3. Pathogen
4. Allergen
5. Hygiene

1. Health — Health is defined as a state of complete physical, mental and social well-being, and not merely an absence of disease or infirmity.

2. Disease — Any physical or functional change in the body from a normal state which causes discomfort or disability is called a disease.

3. Pathogen — Pathogens are disease-causing germs (microorganisms) that have the potential to cause infectious diseases. For example, viruses, bacteria, protozoans etc.

4. Allergen — Allergens are substances that can trigger an unpredictable allergic reaction in individuals.

5. Hygiene — Hygiene is defined as science and practice of maintaining good health.