tertiary

The definition of tertiary is third.

(adjective)

An example of tertiary is the third level of seats in a theater.

See tertiary in Webster's New World College Dictionary

adjective

of the third rank, order, formation, stage, etc.; third
Chem.
1. third in order or type; involving the substitution of three atoms or radicals
2. characterized by or designating a carbon atom or group attached to three other carbon atoms or groups in a chain or ring
Geol. designating or of the first geologic period of the Cenozoic Era, usually subdivided into the Paleogene and the Neogene and characterized by the formation of major mountain ranges, the first grasses and grasslands, and the development of mammals as the dominant animal
Linguis.
1. designating, of, or being the third strongest of the four phonemic degrees of stress
2. a mark used to indicate this
R.C.Ch. of a Third Order
Zool. tertial

Origin: L tertiarius < tertius, third

noun pl. tertiaries

See tertiary in American Heritage Dictionary 4

adjective

Third in place, order, degree, or rank.
Of, relating to, or designating the short flight feathers nearest the body on the rear edge of a bird's wing.
Chemistry
a. Of or relating to salts of acids containing three replaceable hydrogen atoms.
b. Of or relating to organic compounds in which a group, such as an alcohol or amine, is bound to three nonelementary radicals.
Tertiary Of or belonging to the geologic time, system of rocks, or sedimentary deposits of the first period of the Cenozoic Era, characterized by the appearance of modern flora and of apes and other large mammals. See Table at geologic time.

noun pl. ter·ti·ar·ies