terti

Terti is a linguistic stem derived from the Latin tertius, meaning "third." It is not commonly used as an independent English word but appears as a root in a range of terms that denote order, level, or sequence. The most frequent derivatives use the combining form terti- in the adjective tertiary, as in tertiary education or tertiary care, and in the noun phrase tertiary sector of an economy. In biochemistry and molecular biology, the same root appears in tertiary structure, referring to the three-dimensional conformation of a protein or other macromolecule.

In geology, the historical term Tertiary referred to a broad geologic interval spanning roughly 66 to 2.6 million years ago. In modern geology, the period has been subdivided, with Paleogene and Neogene used in place of the traditional Tertiary; however, the historical term persists in literature and certain regional or older references.

Etymology: tertiary traces to Latin tertius 'third', via the Old French tertier and English forms, consolidating into the English combining form terti- that begins many related words.

See also: tertiary, tertian, tertius.