The tenth book of Khuddaka Nikāya of the Sutta Pitaka containing tales of the former births of the Buddha. The Jātaka also forms one of the nine angas or divisions of the Buddha's teachings, grouped according to the subject matter (DA.i.15, 24).
The canonical book of the Jātakas (so far unpublished) contains only the verses, but it is almost certain that from the first there must have been handed down an oral commentary giving the stories in prose. This commentary later developed into the Jātakatthakathā.
Some of the Jātakas have been included in a separate compilation, called the Cariyā Pitaka. It is not possible to say when the Jātakas in their present form came into existence nor how many of these were among the original number. In the time of the Culla Niddesa, there seem to have been five hundred Jātakas, because reference is made to pañcajātakasatāni (p.80; five hundred was the number seen by Fa Hsien in Ceylon (p.71)). Bas-reliefs of the third century have been found illustrating a number of Jātaka stories, and they presuppose the existence of a prose collection. Several Jātakas exist in the canonical books which are not included in the Jātaka collection. For a discussion on the Jātakas in all their aspects, see Rhys Davids Buddhist India, pp.189ff.
The Dīghabhānakas included the Jātaka in the Abhidhamma Pitaka. (DA.i.15; the Samantapāsādikā (i.251) contains a reference to a Jātakanikāya).
The Jātaka consists of twenty-two sections or nipātas.