thought

The Old English noun þōht comes from the verb þencan, to think, which traces to Proto-Germanic þanhtaz. The Indo-European root behind it, tong-, carried a sense of feeling or seeming as much as pure cognition. Old English also had þyncan, a separate verb meaning to seem or appear. The two looked so similar that medieval writers regularly confused them, producing the fossil methinks, which uses the old impersonal construction.

By Middle English, around 1200, þōht had settled into the form thoght, then thought. The word meant the act of thinking, a mental conception, or the capacity for reflection. Middle English writers used it broadly: a sudden thought, a considered opinion, a prolonged meditation. Chaucer in the 14th century used thought to mean anxiety or grief, a sense now largely lost.

The noun's long stability in English is remarkable. It has not changed its core meaning since Old English. The 17th-century philosophers who built the vocabulary of modern epistemology used thought as a foundation: Descartes's cogito ergo sum, the English debates over Locke's Essay Concerning Human Understanding, all relied on an unambiguous central term. The word held its shape while the arguments around it exploded.

German's equivalent, Gedanke, from a related Germanic root, shows how closely the northern languages tracked each other. Dutch gedachte and Swedish tanke share the same ancestry. English thought shed the ge- prefix common to German and Dutch, giving it the clean monosyllabic form it still carries. The word is now among the 500 most common in the language.