* Gravity: The force of attraction between any two objects with mass.

* Gene: A unit of heredity that is transferred from a parent to offspring and determines some characteristic of the offspring.

* Geology: The study of the Earth's physical structure and substance, its history, and the processes that act on it.

* Genus: A taxonomic rank below family and above species.

* Gases: A state of matter characterized by having no fixed shape or volume.

* Genome: The complete set of genes or genetic material present in a cell or organism.

* Geotropism: The growth of a plant in response to gravity.

* Gyroscope: A device used to measure or maintain orientation, often used in navigation systems.

Which one is the most relevant to your needs? Let me know and I can give you a more specific explanation.