Anhydride

Part of speech: noun

Definitions

1. A chemical species that is created by the elimination of water molecules from acids or bases, often participating in subsequent chemical transformations
2. A substance that emerges from the loss of water from acidic or basic compounds, commonly engaging in further reactions with water
3. A chemical compound formed through the removal of water from acids or bases, typically involved in further reactions with other substances

Etymology: The name carries its own explanation: "anhydride" is built from "an-", a Greek prefix meaning "without", plus "hydride", a term for a compound containing hydrogen. Literally, an anhydride is a compound "without water." The "an-" comes from Ancient Greek "ă-" (a negating prefix, the same element that appears in words like "anarchy"), and "hydro-" comes from Greek "hŭdro-", the combining form of "hūdōr," meaning water. The same watery root shows up in "hydrogen" and "hydrant." The chemistry behind the name is that these compounds are what remain when water is removed from a parent substance, such as two molecules of an acid losing a molecule of water. Chemists used the "without water" idea because the product is, in effect, the acid or base minus its water. The "-ide" ending comes from Latin "-idus" through French, and is the standard suffix chemists use for simpler binary compounds, which is why "hydride" sits at the heart of the word.