Science

Science word is taken from Greek word 'Scientia'.which means 'to know'.

"The systematic study of the nature and behaviour of the material and physical universe  based on observation, experiment, and measurement, and the formulation of laws to describe these facts in generalterms is called SCIENCE."

Science has basically following branches -
1. Physics
2. Chemistry
3. Biology

Physics

Physics word is taken from Greek word 'Fusis'. Which means 'Nature'.

Physics is the branch of science in which we study about nature, natural principles, natural phenomenons.

Chemistry

Chemistry is a physical science, and it is the study of the properties of and interactions between matter and energy. In other words, chemistry is a way to study the properties, characteristics, and physical and chemical changes of matter.

chemistry is known as the central science because it touches all other natural sciences, like biology, physics, geology, and more.

Biology

Biology is the science of life. Biology is derived from the Greek words "bios" (life) and "logos" (study). In which we study about the structure, function, growth, origin, evolution and distribution of living organisms.