teach

Etymology 1

From Middle English techen, from Old English tǣċan (“to show, declare, demonstrate; teach, instruct, train; assign, prescribe, direct; warn; persuade”), from Proto-West Germanic *taikijan, from Proto-Germanic *taikijaną (“to show”), from Proto-Indo-European *deyḱ- (“to show”). Cognate with Scots tech, teich (“to teach”), German zeigen (“to show, point out”), zeihen (“accuse, blame”), Gothic 𐌲𐌰𐍄𐌴𐌹𐌷𐌰𐌽 (gateihan, “to announce, declare, tell, show, display”), Latin dīcō (“speak, say, tell”), Ancient Greek δείκνυμι (deíknumi, “show, point out, explain, teach”), Sanskrit दिशति (diśati, “to point out, show, tell, teach”). More at token.

verb

1. (ditransitive) To pass on knowledge to.
   Can you teach me to sew?  Can you teach sewing to me?
2. (intransitive, stative) To pass on knowledge generally, especially as one's profession; to act as a teacher.
   She used to teach at university.
3. (ditransitive) To cause (someone) to learn or understand (something).
   Deep Blue taught us a great deal about the power of the human mind precisely because it could not reproduce the intuitive and logical leaps of Kasparov’s mind. A truly synthetic cell, built from scratch or even from preexisting components, will be a cell without ancestry, and it, too, will teach us a great deal about the underlying complexities of life without actually reproducing them. 2013 September-October, Rob Dorit, “Making Life from Scratch”, in American Scientist
4. (ditransitive) To cause to know the disagreeable consequences of some action.
   I'll teach you to make fun of me!
5. (obsolete, transitive) To show (someone) the way; to guide, conduct; to point, indicate.
   ‘The bliss is there’, mumbled the old man and taught to Heaven.
   c1450, Mandeville's Travelsː Blessed God of might (the) most.. teach us the right way unto that bliss that lasteth aye.
   c1460, Cursor Mundiː Till thy sweet sun uprose, thou keptest all our lay, how we should keep our belief there taught'st thou us the way.

Etymology 2

Clipping of teacher.

noun

1. (informal, usually as a term of address) teacher