Nikāya

Nikāya is a Pāli word meaning “volume”. It is often used like the Sanskrit word āgama to mean “collection”, “assemblage”, “class” or “group” in both Pāḷi and Sanskrit. It is most commonly used in reference to the Pali Buddhist texts of the Tripitaka namely those found in the Sutta Piṭaka. It is also used to refer to monastic lineages, where it is sometimes translated as a ‘monastic fraternity’.

The term Nikāya Buddhism is sometimes used in contemporary scholarship to refer to the Buddhism of the early Buddhist schools.
the Sutta Piṭaka is broken up into five nikāyas:

• the Dīgha Nikāya, the collection of long (Pāḷi: dīgha) discourses
• the Majjhima Nikāya, the collection of middle-length (majjhima) discourses
• the Samyutta Nikāya, the collection of thematically linked (samyutta) discourses
• the Anguttara Nikāya, the “gradual collection” (discourses grouped by content enumerations)
• the Khuddaka Nikāya, the “minor collection”

wikipedia/en/Nik%C4%81ya