In an other thread, tsuwm suggest GROK, as a favorite new word. The word is not well established world wide, but it does represent the comprehension of a principle, the cartoon lightbulb going on. Betty Friedan called it "the Click" when you suddenly realize something in full. Epiphany an other is an way this is expressed, and Eureka!--but I guess these express enlightenment- and while that is a kind of knowledge..

there is also street smarts, or being a graduate of the school of hard knocks, and while they are not single words, they do express "hard won knowledge"