It can be defined as a chemical or biological substance with a defined molecular structure which when presented to a living body, binds to the antibodies or T cells and may or may not induce immune response in the host body.

Adjuvant is a substance of natural or chemical origin that enhances the immune response of the body to an antigen presented.

These are proteinaceous molecules produced by immune system of the body in response to entry of an antigen. Antibodies are nothing but immunoglobulins in nature.

It is the ability of a substance to be recognized by the immune system of a living body.

It is the antigenic determinant of an antigen which is the interacting site between an antigen to that of paratope of an antibody.

It is the ability of an antigen to induce immune response in a living body. These antigens inducing immune response are termed as immunogens. All immunogens are antigens, but all antigens are not immunogens.

These are nothing but the first generation vaccines which are produced either by attenuating the live infectious (bacteria or virus) organism (Live attenuated vaccine) or by inactivating the infectious agent (inactivated vaccine).

These are inactivated toxins produced by a bacterium. These can be used for preparation of toxoid vaccines. e.g. tetanus toxoid.

These are the vaccine formulations, which are prepared by isolation of the microorganism of a particular animal host and then administering the same to that particular animal as vaccine. These are also called as autologous vaccine.

These are caused by infectious agents like bacteria, viruses and parasites. These diseases spread from an infected animal to a susceptible host either directly or through indirect contact with the help of any vehicle i.e. vector, fomite etc.

These diseases are nothing but diseases of infectious origin those spread from person to person in a community through air-borne, water-borne, vector borne transmission etc . All communicable diseases are infectious; however, all infectious diseases are not communicable.

These are the infectious diseases which spread from one animal to another through direct contact; through infectious discharges like saliva, urine, faeces and infectious droplets etc.; through ingestion of contaminated food and water or indirectly though contaminated fomites. However, vector borne transmission are not classified under contagious diseases as these can not be transmitted directly from one infected animal to another through direct contact; rather these are communicable diseases.

When the number of cases of a disease increases in a particular geographical area, and spreads rapidly, it is often referred as an epidemic disease.

These diseases are reported from a particular locality or the region over a quite long period.

There is sparse or limited occurrence of a particular disease in a geographical area over a time period.

These are the diseases affecting animal population, of which number of cases increases rapidly in a particular geographical locality.

These are the animal diseases of which cases are constantly reported from a particular geographical area.

The diseases where cases increases rapidly in an alarming fashion across different countries are pandemic diseases

Serosurveillance refers to the serological study that evaluates the presence or absence of a particular infection in a population of a particular geographical area.

It refers to the serological study which is conducted to evaluate the level of antibody titre in a population of a particular geographical area vaccinated against a particular infectious pathogen in regular time interval.