COMBINING FORM

[combining form] n (1884): a linguistic form that occurs only in compounds or derivatives and can be distinguished descriptively from an affix by its ability to occur as one immediate constituent of a form whose only other immediate constituent is an affix (as cephal- in cephalic) or by its being an allomorph of a morpheme having another allomorph that may occur alone or can be distinguished historically from an affix by the fact that it is borrowed from another language in which it is descriptively a word or a combining form