word-forming element meaning "self, one's own, by oneself, of oneself" (and especially, from 1895, "automobile"), from Greek autos, reflexive pronoun, "self, same," which is of unknown origin. It also was a common word-forming element in ancient Greek, as in modern English, but very few of the old words have survived the interval. In Greek, as a word-forming element, auto- had the sense of "self, one's own, of oneself ('independently'); of itself ('natural, native, not made'); just exactly; together with." Before a vowel, it became aut-; before an aspirate, auth-. In Greek it also was used as a prefix to proper names, as in automelinna "Melinna herself." The opposite prefix would be allo-.
"fitted or intended for instruction; pertaining to instruction," 1650s, from French didactique, from Latinized form of Greek didaktikos "apt at teaching," from didaktos "taught," past participle of didaskein "teach," from PIE *dens- "to learn" (source also of Sanskrit dasra- "effecting miracles"). Related: Didactical; didactically.