In the Pāli Canon, particularly, the "Discourse Basket" or Sutta Piṭaka, the meaning of nikāya is roughly equivalent to the English collection and is used to describe groupings of discourses according to theme, length, or other categories. For example, 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"
In the other early Buddhist schools the alternate term āgama was used instead of nikāya to describe their Sutra Piṭakas. Thus the non-Mahāyāna portion of the Sanskrit-language Sutra Piṭaka is referred to as "the Āgamas" by Mahāyāna Buddhists. The Āgamas survive for the most part only in Classical Tibetan and Chinese translation. They correspond closely with the Pāḷi nikāyas