assimilated form of ad- "to, toward, before" before stems beginning in -t-; see ad-. In Old French and Middle English regularly reduced to a-, later restored.
word-forming element meaning "four, having four, consisting of four," a variant of quadri- which was used in Latin especially before -p-, from an older form of the element which perhaps was influenced later by tri-.
the usual form of Latin dis- in Old Italian, Spanish, Portuguese, Provençal, and French. In Middle English, interchanging with dis- (which in a later period displaced it), hence such form as desarmen, desdein, deshonour, desparagen, deschargen, despisen, etc.
assimilated form of com- "with, together" before stems beginning in -l-. In early Latin, com- was assimilated to these as con-, but col- later also was used. Latin words in coll- became col- in Old French and thus in early Middle English but were altered back to coll- with the revival of learning.
word-forming element meaning "art, craft, skill," later "technical, technology," from Latinized form of Greek tekhno-, combining form of tekhnē "art, skill, craft in work; method, system, an art, a system or method of making or doing," from PIE *teks-na- "craft" (of weaving or fabricating), from suffixed form of root *teks- "to weave," also "to fabricate."
before vowels, gluc-, word-forming element used since c. 1880s, a later form of glyco-, from Greek glykys "sweet," figuratively "delightful; dear; simple, silly," from *glku-, a dissimilation in Greek from PIE root *dlk-u- "sweet" (source also of Latin dulcis). De Vaan writes that "It is likely that we are dealing with a common borrowing from an unknown source." Now usually with reference to glucose.
word-forming element meaning "below, beneath," from Latin infra (adverb and preposition) "below, underneath, on the under side, beneath," also "later than; smaller than; inferior to," related to infernus "low, below," from PIE *ndher "under" (source also of Sanskrit adnah "below," Old English under "under, among;" see under). Modern popular use of it dates from the 1920s, as an opposite to super-, often in science fiction. "This use of infra- is scarcely a Latin one" [OED].
word-forming element meaning "man, male, masculine," from Greek andro-, combining form of anēr (genitive andros) "a man, a male" (as opposed to a woman, a youth, or a god), from PIE root *ner- (2) "man," also "vigorous, vital, strong."
Equivalent to Latin vir (see virile). Sometimes in later use it was equivalent to Greek anthrōpos, Latin homo "a person, a human being," and in compounds it often retain this genderless sense (e.g. androcephalous "having a human head," said of monsters including the Sphinx, which in Greece was female).
word-forming element meaning "not, opposite of, without" (also im-, il-, ir- by assimilation of -n- with following consonant, a tendency which began in later Latin), from Latin in- "not," cognate with Greek an-, Old English un-, all from PIE root *ne- "not."
In Old French and Middle English often en-, but most of these forms have not survived in Modern English, and the few that do (enemy, for instance) no longer are felt as negative. The rule of thumb in English has been to use in- with obviously Latin elements, un- with native or nativized ones.