Merriam-Webster Collegiate Dictionary - combining form

 noun  Date: 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 derived from an independent word (as electro- representing electric in electromagnet or para- representing parachute in paratrooper) 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 ~ (as French mal giving English mal- in malodorous)