What is a giggaannum?

A gigaanum (Ga) is a unit of geological time equivalent to one billion years. It is used primarily in the fields of geology and planetary science to describe significant periods in Earth's history or the age of celestial bodies. The term is derived from the prefix "giga," meaning billion, combined with "annum," which means year in Latin. Gigaanums are often used to discuss the age of the Earth, which is about 4.5 gigaanum old.