tertiær

Tertiär, or tertiär, is an adjective used in several European languages to mean third or tertiary. The form with a diacritic, such as tertiär (Swedish) or tertiær (Danish/Norwegian), reflects language-specific spelling of the same root. The term derives from the Latin tertius, meaning "third," and is used across different fields to indicate a later or secondary level in a sequence.

In geology, Tertiary was historically a major division of the geologic time scale, covering roughly 66 to 2.6 million years ago. Modern stratigraphy typically divides this interval into the Paleogene and Neogene periods, and many current charts avoid using the formal label Tertiary. The term remains common in older literature and in some regional contexts.

In education, tertiary education refers to post-secondary institutions and programs, including universities, colleges, and vocational schools, that follow secondary education. The term distinguishes higher-level study from primary and secondary education.

In medicine and health care, tertiary can describe a late or advanced stage of a disease (tertiary syphilis is a historical example) or the level of specialized care provided at tertiary care centers, such as major hospitals offering advanced diagnostics and treatments.

In economics, the tertiary sector denotes services, including retail, finance, education, health, and other professional services. This sector is contrasted with the primary (extractive) and secondary (manufacturing) sectors and is a core component of many modern economies.

Overall, tertiary serves as a cross-domain term for “third” or “advanced/servicing,” with its precise meaning varying by language and field.