I remember asking myself one late night while drinking tea, "What is knowing?" and I repeated this question to myself a few times and realized I wasn't entirely sure.
This is one of those situations where ten pages of discussion can save you two minutes in the library.
The standard philosophical definition of "knowledge" is a "justified, true, belief."
Allow me to unpack that :
* Justified : for something to be "knowledge," you need to have a reason to believe it; just making stuff up isn't a valid path to knowledge, but reasoning and evidence are. Note that "justification" isn't the same as "proof"; a justification can simply be along the lines of "very probable," (I 'know' that the tallest building in DC is the Washington Monument, because it was when I was there several months ago and I haven't heard about it being knocked down.)
* True : you can't 'know' something that isn't true (no matter how compelling the justification is).
* Belief : To know something, you must actually hold that it's true.
You might then ask, well is it appropriate to equate defined words with knowledge? Is language, with it's defined words, a form of knowledge?
Not in this framework; beliefs are propositions; you can't "know" the definition of a word -- what you know is that the definition of a word is such-and-such. Which makes more sense, because you can't know the definition without knowing what the definition is.
There's a lexical ambiguity in English where you can use the word "know" to mean acquantainceship or familiarity -- "I know Baltimore fairly well, but I've only been to Annapolis twice in my life." That's not generally considered to be "knowledge" in a philosophical sense.