Knowledge is everything you know and understand. General knowledge, to my knowledge, common knowledge.
It is uncountable, so nobody has knowledges — a fact that catches out learners constantly. To my knowledge is a hedge meaning as far as I am aware. Common knowledge means so widely known that nobody need be told. In philosophy, the classic definition of knowledge as justified true belief has been argued about for two and a half thousand years. Note the Knowledge, the London taxi test.
1nounknowledgeEverything you know and understand.
“He has a good knowledge of European history.”
knowledge is what is known.
Middle English knowleche is know plus an obscure suffix -leche, which appears in almost no other surviving word. The formation is a genuine puzzle.
Proto-Indo-European
*ǵneh₃-
Middle English
knowleche
English, today
knowledge
Built from
From Middle English knowleche, knaweleche, cnawlece (“knowledge”), from knowen (“to know, recognise”) + -leche. Related to Middle English knowlechen (“to find out, acknowledge”). For more on the Middle English suffix -leche, compare freelage. Compare also Old English cnāwelǣċ, cnāwelǣċing (“acknowledging, acknowledgement”).
Etymology from Wiktionary, CC BY-SA