[Paal Gulli]

Incorrect.

There are four genders: masculine, feminine, common and neuter.

But there are only two sexes: male and female.

[Fightin Whitey]

There are four genders: masculine, feminine, common and neuter. But there are only two sexes

Yes, exactly. Tip o' the hat to you.

[Svartalfiar]

There are four genders: masculine, feminine, common and neuter.

Huh? Common? What language are you basing this off of? And what is the common gender? What is its opposite?