The root word geo- comes from the Greek word gē or gaia, which means "earth" or "land".
geology: study of the physical or solid “Earth”
geologist: one who studies the solid parts of the “Earth”
geography: study of the nations and peoples of the “Earth”
geometry: the branch of mathematics concerned with the properties and relations of points, lines, surfaces, and solids.
geocentric: of an “Earth”-centered Universe