TErrestrial

Terrestrial is an adjective derived from Latin terra, meaning land or Earth. In general usage, the term denotes things related to the Earth or to land as opposed to water or sky. In science and everyday language, the word is applied in several domains.

In biology and ecology, terrestrial refers to organisms that live on land as opposed to aquatic environments or aerial habitats. Terrestrial plants include a wide range of species adapted to soil, weather, and gravity. Terrestrial animals include many land vertebrates and invertebrates; some species are strictly terrestrial, while others are partially terrestrial or spend significant time on land.

In astronomy, terrestrial describes rocky, Earth-like planets. Terrestrial planets, such as Mercury, Venus, Earth, and Mars, have solid surfaces and relatively small sizes compared with gas giants, with metal cores and silicate crusts. They differ from gas giants in appearance, density, and atmospheres.

In technology and media, terrestrial can describe ground-based systems, such as terrestrial television and terrestrial radio, which transmit signals from networks on the Earth’s surface rather than from orbiting satellites. In measurement and geodesy, terrestrial references describe models anchored to the Earth's surface.

The word is also used more broadly to mean worldly or non-spiritual in some contexts, though this usage is less common in scientific writing.