Spiral galaxy : A galaxy in which the stars and gas clouds are concentrated mainly in one or more spiral arms.

Satellites : Heavenly bodies that revolve around large planets, like the Moon orbiting Earth.

Asteroid : A small. rocky planetary body orbiting the sun.

Milky Way : The galaxy which contains the Solar System, which comprises our home planet - Earth

Nebula : A giant cloud of dust and gas in space.

Terrestrial planet : Also known as rocky planet that is primarily composed of silicate rocks or metals c.g., the four inner planets, viz. the Mercury, Venus, Earth and Mars.

Oblate spheriod : The earth’s shape that bulges at the equator and is somewhat squashed at the poles.

Curvature : The fact of being curved or the degree to which something is curved, cg. the curvature of the earth.

Sphericity : It is a measure of how closely the shape of an object resembles that of a perfect sphere.

Biosphere : The layer of planet earth where life exists.

Ecosystem : Group of organisms and environment with which organisms interact.

Environment : The surroundings or conditions in which a person, animal or plant lives or operates.

Photochemical process : A chemical reaction initiated by the absorption of energy in the form of light.

Photosynthesis : The process used by green plants to convert light energy into chemical energy.

Solar radiation : The radiant energy emitted by the sun from a nuclear fusion reaction that creates electromagnetic energy.

Transpiration : The process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers.

Human habitat : The land of the earth that supports human life.

Meteorite : Any particle of solid matter that has fallen to the earth, the moon. or another planet from space.

Milky Way : The name of our galaxy.

Photosynthesis : The reaction of carbon dioxide and water in green plants, under the influence at certain wavelengths of visible light, which releases oxygen and produces energy and rich organic material (sugar and starch).

Zenith : The point vertically above the observer.

Antipode : ln geography, the antipode of any place on earth is the point on the earth surface that is diametrically opposite to it.