word-forming element meaning "small in size or extent, microscopic; magnifying;" in science indicating a unit one millionth of the unit it is prefixed to; from Latinized form of mikros, Attic form of Greek smikros "small, little, petty, trivial, slight," perhaps from PIE *smika, from root *smik- "small" (source also of Old High German smahi "littleness"), but Beekes thinks it a Pre-Greek word.
word-forming element meaning "many, much, multi-, one or more," from Greek polys "much" (plural polloi), from PIE root *pele- (1) "to fill," with derivatives referring to multitudinousness or abundance. Equivalent to Latin multi-, it is properly used in compounds only with words of Greek origin. In chemical names, usually indicating a compound with a large number of atoms or molecules of the same kind (such as polymer).
word-forming element meaning "half, half-sized, partial," used in English from mid-14c., especially in technical terms from French, from Old French demi "half" (12c.), from Late Latin dimedius, from Latin dimidius "half, one-half," which contains the elements dis- "apart" (see dis-) + medius "in the middle, between; from the middle," as a noun "the middle;" from PIE root *medhyo- "middle." Formerly also demy-, and in early use often written as a separate word.
word-forming element meaning "bad, ill; hard, difficult; abnormal, imperfect," from Greek dys-, inseparable prefix "destroying the good sense of a word or increasing its bad sense" [Liddell & Scott], hence "bad, hard, unlucky," from PIE root (and prefix) *dus- "bad, ill, evil" (source also of Sanskrit dus-, Old Persian duš- "ill," Old English to-, Old High German zur-, Gothic tuz- "un-"), a derivative of the root *deu- (1) "to lack, be wanting" (source of Greek dein "to lack, want").
Very productive in ancient Greek, where it could attach even to proper names (such as dysparis "unhappy Paris"); its entries take up nine columns in Liddell & Scott. Among the words formed from it were some English might covet: dysouristos "fatally favorable, driven by a too-favorable wind;" dysadelphos "unhappy in one's brothers;" dysagres "unlucky in fishing;" dysantiblepos "hard to look in the face."
The "sh" sound did not exist in Old French, therefore French scribes after the Norman conquest often represented it with -ssh- in medial and final positions, and sch- in initial positions (schape, schamful, schaft for shape, shameful, shaft). But the spelling -sh- has been standard since Caxton, probably as a worn-down form of Middle English -sch-.
In some East Anglian texts from 14c.-15c., x- is used (xal, xulde for shall, should), which would have given the language a very different look had it prevailed, but the London-based sh- ended up as the standard form. The same Germanic sound has become, by natural evolution, modern German and Dutch sch-, Scandinavian sk-.
word-forming element meaning "old," from Greek presby-, combining form of presbys "elderly, aged," as a noun, "elder, old man," which is of uncertain and much debated origin and phonetic development (some Doric forms have -g- in place of -b-). The first element is likely *pres- "before, in front" (from PIE root *per- (1) "forward," hence "in front of, before, first"). Perhaps the whole originally meant "one who leads the cattle," from the root of bous "cow." Watkins, however, has it from PIE *pres-gwu- "going before," with second element from root *gw-u- "going," a suffixed form of root *gwa- "to come."
Also used with native and imported elements to form verbs from nouns and adjectives, with a sense "put in or on" (encircle), also "cause to be, make into" (endear), and used as an intensive (enclose). Spelling variants in French that were brought over into Middle English account for parallels such as ensure/insure, and most en- words in English had at one time or another a variant in in-, and vice versa.