On-tŏl'o-ġy, n.

[Fr. ontologie, It. & Sp. ontologia, from Gr. οντα, the things which exist, pl. neut. of ὤν, ὄντος, being, p. pr. of εἶναι, to be, and λόγος, discourse.] That part of the science of metaphysics which investigates and explains the nature and essential properties and relations of all beings, as such.