Are there any rules for the plural form?
I was reading this article about the plural in german
http://germanforenglishspeakers.com/nouns/gender-and-plurals/
How do I know which plural form I'll use? Is there some pattern like the rules to know if the article is der, die or das?

Question

Answer

Of course, there are rules how nouns build their plural in German but it's not so simple as in Portuguese or English. There are a lot of rules and it will be quite difficult to learn them for a short period of time. The same situation with gender. One has to learn and remember gender of each noun although there are rules helping people to know what gender a noun is. Again the rule is quite long. If you are interested in that, you'd better read a grammar book and  write out every noun with its plural form and in a while the rule will be clear to you.