You can't look up just one definition in the U.C.C. or Black's Law Dictionary and expect, "Yeeeah Boi!  There it is!"  Nope. They ain't gonna make things that easy.  No.  At the end of each of these definitions are references pointing you to other things, like "See Instrument", or "See Check", or "See draft", or "See Bill of Exchange" or "See this" or "See that" ...  --- You have to look them ALL up!  It's a "Merry-go-round" ---a maze!  You have to "follow the white rabbit" until you come round full circle to your starting point again.  They've kept this thing a "secret" out in the open for 80 years for good reason: the average person is too lazy or stupid to chase down the prize.  Don't go talking to these clowns "on the inside" until you feel confident you know what you're talking about -- and that may take a while.  Download the entire U.C.C. and at least a couple editions of Black's Law Dictionary (I have 4 editions) to your computer so you can browse these things anywhere, anytime.  I also have the entire U.S. Code, Bouvier's Maxims of Law and the 1914 3-volume Encyclopedia of Law set, etc., etc.  No, you and I are probably not going to read them all, but we have them at our fingertips for references.