tertiary
Pronunciation: /ˈtəːʃ(ə)ri/
adjective
- 1third in order or level: the tertiary stage of the disease
- chiefly British relating to or denoting education at a level beyond that provided by schools, especially that provided by a college or university.
- relating to or denoting the medical treatment provided at a specialist institution: patients in tertiary care
noun

Origin:
mid 16th century (in tertiary (sense 2 of the noun)): from Latin tertiarius 'of the third part or rank', from tertius 'third'