From Greek 'didaskein' (to teach) — initially neutral for 'instructive,' it gradually acquired overtones of pedantry.
Intended to teach or instruct; having the manner of a teacher, sometimes with a connotation of being overly moralistic or preachy.
From Greek 'didaktikos' (apt at teaching, instructive), from 'didaskein' (to teach, to instruct), from a reduplicated form of PIE *dens- (to learn, to teach). The Greek root 'didaskein' is unusual in being both active and causative — it means both 'to learn' and 'to cause to learn (teach).' The word entered English via French 'didactique' in the mid-seventeenth century, initially as a neutral term for instruction but gradually acquiring negative overtones of excessive moralizing. Key roots: didaskein (Greek: "to teach, to instruct"), *dens- (Proto-Indo-European: "to learn, to teach").
An 'autodidact' (self-taught person) combines Greek 'autos' (self) with the same root. The early Christian text called the 'Didache' (The Teaching) also shares it. Greek 'didaskein' is a reduplicated form — the 'di-' at the start echoes the root, a pattern common in ancient Indo-European languages for intensive or habitual actions.