What is Earth ?
Earth is (noun) 1. also Earth the planet on which we live The earth goes round the sun once in twenty-four hours. The space shuttle came back to earth safely. it costs the earth it costs a great deal of money (informal.) It wouldn’t cost the earth to have the house repainted. 2. soil, a soft material made up of minerals and rotting vegetable matter, which plants grow in Put some earth in the plant pot and then sow your cucumber seeds. 3. a hole where a fox lives to run someone to earth to find someone after a difficult search We finally ran him to earth in Mexico. (verb) to connect an electrical appliance to the earth Household appliances should be properly earthed. (NOTE: The US term is to ground.)
source: Easier English, Student Dictionary Upper Intermediate Level