From The Dhamma Encyclopedia
Phassa: fr. phusati to touch: 'sense-contact', contact. The term samphassa is used in compounds, e.g. in the following: ';T'here are 6 classes of sense-contact: visual contact cakkhu-samphassa contacts of hearing, smelling, tasting, bodily tactile contact and mental contact; M. 9. A twofold division occurs in D. 15: patigha samphassa contact by sensorial reaction', and adhivacana-samphassa verbal or conceptual, i.e. mental contact'.
phassa does not signify physical impact, but is one of the 7 constant mental properties of consciousness cetasika and belongs to the group of mental constructions sankhāra-khandha In lists of both these categories it is generally mentioned first e.g. Dhs. 1: M. 9, due to its fundamental position in the cognitive process In M. 18 it is thus defined:;Dependent on the eye and the forms, visual-consciousness arises; the coming-together of the three is sense-contact; similarly stated in the case of the other 5 senses, including mind. In the dependent origination, it is conditioned by the six sense-sources and is a conditioning factor of feeling see: paticca-samuppāda, 6. Its relation to mind-and-body nāma-rūpa is described in D. 15, and its influence on feeling and wrong views, in D. 1 at the end. - It is one of the 4 nutriments āhāra, and the first factor in the pentad of sense-contact phassa-pañcamaka together with feeling, perception, intention and consciousness see Abh. St., p. 47ff.
Being a key function in the mind's contact with the world of objects and being a potential source of defilements, sense-contact is an important subject for reflective insight contemplation as succinctly formulated in many verses of the Sn.: 736/7, 778, 851, 870/72, 923.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.