Build your vocabulary with Merriam-Webster's Word of the Day! Each day a Merriam-Webster editor offers insight into a fascinating new word -- explaining its meaning, current use, and little-known details about its origin.
May 17th, 2015
Episode 198 of 797 episodes
Merriam-Webster's Word of the Day for May 17, 2015 is: terrestrial \tuh-RESS-tree-ul\ adjective 1 : of or relating to the earth or its inhabitants 2 : living or growing on land 3 : belonging to a class of planets that are like the earth (as in density and silicate composition) Examples: The newly discovered fossils include some of the earliest known terrestrial arachnids. "The InSight mission, scheduled to launch in March 2016, will record the first ever measurements of the interior of the red planet, giving scientists detail into the evolution of Mars and other terrestrial planets." Denver Post, November 18, 2014 Did you know? What do terriers, terrariums, and terraces have in common with terrestrial? Terra firma! All of those words derive from the Latin root terra, which means "earth." Of course, terrestrial can refer to anything on or from the Earth, and extraterrestrial describes things (or science fiction creatures) that come from space. And early usage of terrestrial, dating from the 15th century, indeed referred to creatures and other things that pertain to this world, as opposed to the heavens. By the 17th century, however, the word was also being used to describe things found strictly on land, as opposed to those found in the sea or air.