*-iz^²

From Proto-Indo-European *-i-s, the stem-forming suffix of i-stem adjectives. The root often appears in lengthened grade, especially with roots corresponding to Strong class 4 and 5 verbs, though zero-grade formations also occur, especially with diphthongal roots. The type is inherited, but in the Germanic languages the original i-stem inflection was preserved only partly, most clearly in Gothic; elsewhere such adjectives were largely absorbed into the a- or ja-stem adjective classes (Fulk 2018: 215). In function, these formations produced verbal adjectives such as ‘X-able, fit to be X-ed’ and, more rarely, active or agentive adjectives. In the passive/possibilitive use, they are functionally comparable to Proto-Indo-European gerundival adjectives in *-yo-(compare Sanskrit दृश्य (dṛ́śya)), while the active use continues the older i-stem pattern of adjectival agent nouns (Krahe & Meid 1969: 65–67).