Nomenclature is a system of names used in a particular field or subject. Scientists use careful nomenclature to identify plants and animals so that a biologist in Brazil and one in Japan can talk about exactly the same species without confusion. Chemists follow strict nomenclature rules when naming compounds: water's chemical name, dihydrogen monoxide, tells you it contains two hydrogen atoms and one oxygen atom.

Nomenclature refers to organized systems of labels that follow logical patterns to help you understand what you're looking at. Good nomenclature uses consistent rules and meaningful structure. In music, the nomenclature of note values (whole notes, half notes, quarter notes) tells you how long to hold each sound. In anatomy, nomenclature helps doctors worldwide use the same terms for bones, muscles, and organs.

You'll encounter nomenclature in almost any specialized subject. Astronomers have nomenclature for naming stars and galaxies. Meteorologists use nomenclature for cloud types: cirrus, cumulus, and stratus. Even video games often develop their own nomenclature for items, character classes, or abilities. When you learn a subject's nomenclature, you're learning the language that experts use to communicate precisely with each other.