Most of the compounds that we have looked at so far involve roots that are free forms. But the vocabulary of English, especially in scientific and technical areas, includes a huge repertoire of compounds that are made up of bound roots, known as combining forms. Here are just a few:

(23) anthropology, sociology, cardiogram, electrocardiogram, retrograde, retrospect, plantigrade

For most of these, the meaning of the whole is clearly determinable from that of the parts: for example, anthrop(o)- ‘human’ plus -(o)logy ‘science or study’ yields a word that means ‘science or study of human beings’, and planti- ‘sole (of foot)’ and -grade ‘walking’ yields a word meaning ‘walking on the soles of the feet’. This semantic predictability is crucial to the coining of new technical terms using these elements.

Apart from containing bound roots, anthropology differs in two other ways from most compound nouns. Firstly, it has a central linking vowel -o- that cannot conclusively be assigned to either root. In this respect it resembles many combining-form compounds. Secondly, although it is a noun, its stress is not on the first element – unless the linking -o- belongs there. In this respect it resembles e.g. monogamy, philosophy and aristocracy.

We encountered bound roots that could function as the base for derivational affixation, such as aud- in audible, audition etc. Not surprisingly, some combining forms can function in this way too (in other words, the dividing line between combining forms and other bound roots is not sharp): for example, soci- and electr(o)- from (23) also occur, indeed much more commonly, in social and electric.

Given that combining forms, and the compounds that contain them, are so untypical of compounds in general, it is natural to ask how English has come to acquire them. In fact, they come mostly from Greek or Latin, through deliberate borrowings to supply new needs for technical vocabulary that arose partly from the revival of learning in western Europe in the fifteenth and sixteenth centuries known as the Renaissance, and partly from the industrial revolution of the eighteenth century and its scientific spin-offs.