There are several words in German that occur in two or all three genders, e.g. der/das Kaugummi ‘chewing gum’. Some of these use the differing gender for different meanings, e.g. der See ‘lake’ vs. die See ‘sea’, and the plural form may differ, too. There’s also a number of masculine words that are changing from an -e ending to -en, e.g. der Funke(n), Same(n). Some of these tend to associate slightly different meaning with these variants, e.g. der Drache ‘dragon’ vs. der Drachen ‘kite’. Furthermore, there are synonyms that differ only in one or two sounds or letters but may differ in gender, e.g. der Sandkasten and die Sandkiste ‘sandpit’.
And then, there is die Socke and der Socken ‘sock’, plural die Socken. Without looking it up, I’m not even sure which one is considered the standard variant (probably the feminine one). As you can see, this case is unlike all the others.
I’d like to know whether there are more pairs like this and if there is a scientific term for it?