(i) Disease: It is the disorder or disturbance, physical or physiological by nature, in the functioning of any part or an organ of the body.
(ii) Health: According to WHO, health is a state of complete mental, physical and social well-being.
(iii) Vaccination: It is the process of protection of the body from communicable diseases by the administration of some agents that mimic the microbe. The agent can be a suspension of killed or attenuated microbes, or a substance that mimics the disease-causing microbes.
(iv) Immunity: It is that characteristic of the body that enables it to fight against the pathogens and other biological agents that enter and harm our body.
(v) Antiseptic: It is a class of chemicals that destroy pathogens but are harmless if used on human beings.
(vi) Cancer: It is a class of disease caused by uncontrolled proliferation of cells without any differentiation.
(vii) Allergy: It is the hypersensitivity of a person to some foreign substance coming in contact with or entering the body.
(viii) Hypersensitivity: The undesirable reactions produced by the normal immune system, such as allergy.
(ix) Immunisation: It is the process by which individuals are made immune against various diseases.
(x) Disinfectant: It is a general anti-biological substance used to kill pathogens. It may cause harm to skin and body.
(xi) Penicillin: The first antibiotic to be used effectively to treat systemic bacterial diseases. It is obtained from a fungus Penicillium notatum. It primarily kills gram-positive bacteria and some gram-negative bacteria.
(xii) Sulphonamide drugs: These drugs inhibit the growth of bacteria. Sulphonamides have a high medical value and is readily absorbed by digestive system.
(xiii) Acquired disease: Acquired disease is caused by a pathogen or a deficiency disease. It may be communicable or non-communicable. Typhoid and cholera are two examples of communicable diseases, while cancer, allergies and diabetes are examples of non-communicable diseases.
(xiv) Prophylaxis: A series of measures taken to prevent diseases.
(xv) Antibiotic: A chemical substance produced by a microorganism that is capable of destroying or inhibiting the growth of other microorganisms.