Class I/II affix

In phonology and morphology, class I/II affix is a classification of (English) affixes.

Example
The English Class I affixes can cause stress shift (párent-paréntal, prodúctive-productívity), while their class II counterparts are stress neutral (párent-párenthood, prodúctive-prodúctiveness). Furthermore, class I affixes may appear inside class II affixes, but not vice versa (*hopefulity). This generalization is usually referred to as the Affix Ordering Generalization.

Comments
Class I and Class II affixes can be distinguished in terms of their different phonological and morphological properties. The distinction between Class I and Class II affixes is equivalent to that between formative-boundary and word-boundary affixes (Chomsky & Halle, 1968), Level I and Level II affixes (Pesetsky 1979, Kiparsky 1982), and Stratum I and Stratum II affixes (Halle & Vergnaud 1987).

Link
Utrecht Lexicon of Linguistics