Ākāsa: 'space', is, according to Com., of two kinds: 1. limited space paricchinnākāsa or paricchedākāsa, 2. endless space anantākāsa, i.e. cosmic space.
1. Limited space, under the name of ākāsa-dhātu space element, belongs to derived materiality see: khandha Summary I; Dhs. 638 and to a sixfold classification of elements see: dhātu M. 112, 115, 140. It is also an object of kasina meditation. It is defined as follows: The space element has the characteristic of delimiting matter or form. Its function is to indicate the boundaries of matter. It is manifested as the confines and container of matter or form; or its manifestation consists in being untouched by the 4 great elements, and in holes and openings. Its proximate cause is the matter delimited. It is on account of the space element that one can say of material things delimited that 'this is above. below, around that' Vis.M XIV, 63.
2. Endless space is in Atthasālini called ajatākāsa unentangled', i.e. unobstructed or empty space. It is the object of the first formless absorption see: jhāna, the sphere of Infinite space ākāsānañcāyatana. According to Abhidhamma philosophy, endless space has no objective reality being purely conceptual, which is indicated by the fact that it is not included in the triad of the advantageous kusalatika, which comprises the entire reality. Later Buddhist schools have regarded it as one of several unconditioned or uncreated states asankhata dharma - a view that is rejected in Kath. see: Guide. p. 70. Theravāda Buddhism recognizes only Nibbāna as an unconditioned element asankhata dhātu see: Dhs. 1084.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.