A linking vowel.
This appears as the final vowel of many prefixes, such as chloro-, Indo-1, pneumo-, schizo-, and techno-. It comes ultimately from its use as a linking vowel in classical Greek combinations, which were borrowed into Latin and thereafter arrived in English via French. It is often used in English as a connecting vowel irrespective of the source of the word elements it links. However, it is often left off if the following element begins with a vowel (as, for example, with phlebo-, a vein, where the -o- is lost in forming phlebitis, inflammation of the walls of a vein). In English the vowel also often acts as a link between a stem and an ending, as in cottonocracy or speedometer. In this book it is the Greek source stem that is decisive in placing an ending in its alphabetical sequence, so that entries (to take two common examples) are listed as -cracy rather than -ocracy and -logy rather than -ology; however, -onym appears in that form because it derives from Greek onoma, name. Entries are cross-referenced where confusion might arise.