Old English eorþe "ground, soil, dry land," also used (along with middangeard) for "the (material) world" (as opposed to the heavens or the underworld), from Proto-Germanic *ertho (cf. Old Frisian erthe "earth," Old Saxon ertha, Old Norse jörð, Middle Dutch eerde, Dutch aarde, Old High German erda, German Erde, Gothic airþa), from PIE root *er- (2) "earth, ground" (cf. Middle Irish -ert "earth"). The earth considered as a planet was so called from c.1400.
Any of several metallic oxides, such as alumina or zirconia, from which it is difficult to remove oxygen. No longer in technical use.
Note: The Earth was formed at the same time as the sun, about 4.6 billion years ago.
Note: It consists of an inner core made of iron and nickel, an outer core of liquid metal, a mantle, and, on the outside, a crust.
Note: The surface of the solid Earth is in a state of constant change as the rock is moved around by the processes of plate tectonics.
Note: On the Earth's surface, the oceans and the continents form the stage on which the evolution of life takes place. The atmosphere above the surface circulates, producing the daily weather.