about gender nouns

Question

Hello, I have a question about feminine and masculine nouns. I learned from the reference that masc ones end in /o or e or other vowels and fem ones end in /a or other consonants /d, /z, or /ion. Also, usually words can be changed into other form of gender nouns. But I can't find how to change them into others. all I know is that nouns that are fem forms sould be changed into /o to be masc and masc ones sould be /a as it is. But how should the other forms be varied? I'll appreciate if you explain the ways for me.

Answer 1

Also, usually words can be changed into other form of gender nouns.

Not true. Some nouns (mostly referring to occupations/professions) have both masculine and feminine forms and a few nouns (e.g. "corte") also exist in both forms but with different meanings. However, usually nouns have one (and only one) gender.

Answer 2

http://www.studyspanish.com/lessons/genoun1.htm