Hi, I would like show how to check a value is defined in an object or not. I decided to post this to show the usages of found?, value?, in and get functions. Here is the situation, O is an object, there a two words defined in O. O: context [A: 3 B: none] B is defined and its value is none. C is not defined in O. And that is what I want to show. You can try using get and found? functions: found? get in o 'A >> true found? get in o 'B >> false found? get in o 'C >> false This is because found? simply tests the value is none or not. (Note that false and none are different in Rebol. "found? false" will return true) So we could not recognize the word B is defined or its value is none. Same question is for C. You can get value of a word inside O using get: get in o 'A >> 3 get in o 'B >> none get in o 'C >> none This is why we could not use found? and get together. So you may thing that we can use value? function. "value? returns TRUE if the word has been set." the document says. value? get in o 'A >> true value? get in o 'B >> true value? get in o 'C >> true Hmm.. this is because "get in o 'C" returns none. And none IS a value in Rebol. get in o 'C >> none value? none >> true So lets look closer, in o 'A >> A in o 'B >> B in o 'C >> none in returns the word itself if it is defind in the object, not its value. This is why we cannot use value? and in together. So our mistake is to use get function. The solution is simple: found? in o 'A >> true found? in o 'B >> true found? in o 'C >> false This is what we want. So we can write this small function: defined?: func [w [word!] o [object!]] [found? in o w] defined? 'A O >> true defined? 'B O >> true defined? 'C O >> false Well, this is how I learnt the meanings of in, get, found? and value? functions. "get a value of a word in an object, if it is none than it is not defined." INCORRECT! And I made this mistake several times when learning Rebol. I hope this will be helpful for beginners.