noumenal (adj.)

"that which can be the object only of a purely intellectual intuition" (opposed to a phenomenon), 1796, a term introduced by Kant, from Greek noumenon "that which is perceived," neuter passive present participle of noein "to apprehend, perceive by the mind" (from noos "mind," which is of uncertain origin). With passive suffix -menos.

suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).