-aceous
(ˈeɪʃəs)
compd. adj. formative f. L. -āce-us, -a, -um, of the nature of, (f. āc- + -e-us, -e-a, -e-um, see -eous) + -ous, favoured by the formal resemblance of the compd. Eng. -ace-ous to the simple L. -āce-us of the nom. masc. Of extensive use in Nat. Hist., where it supplies adjectives, Eng. in form, to the nouns in -ācea, -āceae, as cetaceous, crustaceous, testaceous, rosaceous, ranunculaceous, papilionaceous; also in other words, as setaceous, cretaceous, carbonaceous, saponaceous, argillaceous, coriaceous, herbaceous, membranaceous, etc. Only a few of these represent actual L. words in -āceus, the majority being purely modern and analogical.