I wanted to use the word "gradation" in an email I had to write. In order to be sure that I use it properly I "googled" it. Everything seemed to be OK although I noticed that there are different meanings of this word. So I decided to look this word up in my Cambridge Learner's Dictionary (4th printing 2008) and ... I didn't find it. Is there something wrong with this word?
P.S. I wanted to use it for a place in an ordered scale.