When somebody says he is an amateur photographer, there is a high chance of a misunderstanding. The dictionary defines amateur in two ways: someone who engages in a pursuit as a pastime rather than as a profession, OR, one lacking in competence or experience in an art or science. Unfortunately most people tend to associate an amateur with the second definition.
Personally, I like to think of an amateur as someone who does something for the love of it. In the mid-nineteenth century an amateur was a highly regarded gentleman who pursues a pastime for the love of it. I wonder how many non-professional photographers take pride in being called an amateur! Or how many "serious amateurs" would get offended if referred to in this way!