I am all at sea when it comes to differentiate the two "gold" & "golden"? As in this idiom, which one is the better choice? Furthermore, do we have a strict discipline as when to use "gold" and the other in related circumstances? I know there are "gold fish", "gold medal", "golden necklace"... Gee, are the medal and the necklace all made from gold? Why the different choices of words? Thank you in advance.