think

Etymology 1

From Middle English thinken, thynken, thenken, thenchen, from Old English þenċan, from Proto-West Germanic *þankijan, from Proto-Germanic *þankijaną (“to think”), from Proto-Indo-European *teng- (“to think, feel, know”). Cognate with Scots think, thynk (“to think”), North Frisian teenk, taanke, tanke, tånke (“to think”), Saterland Frisian toanke (“to think”), West Frisian tinke (“to think”), Dutch denken (“to think”), Afrikaans dink (“to think”), Low German denken, dinken (“to think”), German denken (“to think”), Danish tænke (“to think”), Swedish tänka (“to think”), Norwegian Bokmål tenke (“to think”), Norwegian Nynorsk tenkja (“to think”), Icelandic þekkja (“to know, recognise, identify, perceive”), Latin tongeō (“know”).

verb

1. (transitive) To ponder, to go over in one's head.
   Idly, the detective thought what his next move should be.
2. (intransitive) To communicate to oneself in one's mind, to try to find a solution to a problem.
   I thought for three hours about the problem and still couldn’t find the solution.
   Thinks I to myself, “Sol, you're run off your course again. This is a rich man's summer ‘cottage’ and if you don't look out there's likely to be some nice, lively dog taking an interest in your underpinning.” 1913, Joseph C. Lincoln, chapter 1, in Mr. Pratt's Patients
3. (intransitive) To conceive of something or someone (usually followed by of; infrequently, by on).
   I tend to think of her as rather ugly.
   Think of banking today and the image is of grey-suited men in towering skyscrapers. Its future, however, is being shaped in converted warehouses and funky offices in San Francisco, New York and London, where bright young things in jeans and T-shirts huddle around laptops, sipping lattes or munching on free food. 2013-08-03, “Revenge of the nerds”, in The Economist, volume 408, number 8847
4. (transitive) To be of opinion (that); to consider, judge, regard, or look upon (something) as.
   At the time I thought his adamant refusal to give in right.
   I hope you won’t think me stupid if I ask you what that means.
   I think she is pretty, contrary to most people.
   Boxing is thought to be a dangerous sport.
   1865, Henry David Thoreau, Cape Cod, Chapter IX. "The Sea and the Desert", page 182. […] one man showed me a young oak which he had transplanted from behind the town, thinking it an apple-tree.
5. (transitive) To guess; to reckon.
   I think she’ll pass the examination.
6. To plan; to be considering; to be of a mind (to do something).
7. To presume; to venture.

noun

1. (chiefly UK) An act of thinking; consideration (of something).
   I'll have a think about that and let you know.

Etymology 2

From Middle English thinken, thynken, thenken (also thinchen, thünchen), from Old English þyncan (“to seem, appear”), from Proto-Germanic *þunkijaną (“to seem”). Cognate with Dutch dunken (“to seem, appear”), German dünken (“to seem, appear”), Danish tykkes (“to seem”), Swedish tycka (“to seem, think, regard”), Icelandic þykja (“to be regarded, be considered, seem”). More at methinks.

verb

1. (obsolete except in methinks) To seem, to appear.