[910] Which phenomena (dhammā) have form (rūpino)? The four great elements (mahābhūta) and the form (rūpa) derived from the four great elements — these phenomena have form.
Which phenomena are formless (arūpino)? The wholesome (kusala) in the four planes (bhūmi), the unwholesome, the resultant (vipāka) in the four planes, the functional indeterminate (kiriyābyākata) in the three planes, and Nibbāna — these phenomena are formless.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.