I think that we should stop being grammar Nazis and start getting back on topic.
So Germans are grammar nazis, are we? :huh:
I know Der Die and Das can change the meaning of a word completely.
Der Die and Das don't really change the meaning of a word, but they can make the difference between right and wrong. The words they refer too would also have a different ending. For example:
Der Freund = the (male) friend, die Freundin = the (female) friend, (obviously there is no neutrum word for friend). It would be wrong to mix the male article with a female word (e.g. Der Freundin would usually be a mess up). However, the male article may refer to the female noun in some cases. For example in the dativ case: "Was passiert der Freundin?" = "What happens to the (female) friend" the male article refers to the female noun. The German language is completely anarchist if it comes to attaching articles to things which one might expect to be referred to as das. For example "die T¸r" = "the door" is female, while "der Teppich" = "the carpet" is male, and "das Auto" = "the car" is neutral. I don't know which male qualities of a carpet or female qualities of a door differentiate it from the neutral status given to a car

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Usually the feminine "die" is always used in plural (e.g. "die M‰nner" = "the men") but once again we have different articles for the different cases in the plural (e.g. "Was passiert den M‰nnern?" = "What happens to the men?"). It is unnecessarily complex, no doubt about that.