This word is supposed to be insignia for lacking almost everything for a person. Amateur is a sign of experience; it basically refers to a personality, which has been fermented just similar to the wine.

However maturity will not be said referring to a child, simply because such a child does not have experience. Maturity is referred to human personality. For this one can say that such a personality does not act like a child. But when the word preceded by the letter "A" then the meaning will change to mean the opposite. For example one can say that act of such person is amateur. Meaning here that such acts are childish.

DR.HASHIM S.H. BEHBEHANI