What is the main difference between tabemasen and tabenai?

Fredさん、 こんにちは Th e main difference between 食（た）べません and 食（た）べない is that the first one is polite and the latter is casual. So you would use the ません form when you need to be polite. Maybe when you are talking with other adults, strangers or people who are higher in the social hierachy than you i.e. Boss, supervisor. E.g. When your boss offers you sake during dinner and you can't drink sake you would say: すみません。さけはのめません。 I'm sorry. I can't drink sake. But if your friend offers you たこやき（Takoyaki) and you can't eat octopus you can say: ごめん。たこがたべないんだ・の。 Sorry but I　can't eat octopus. *You can use ない+んだ for males. The ない+んだ is used like です but is more colloquial and is used to give an explanation/reason. Girls can use ない+の. Lisa

どもありがと Lisaさん!

Fredさん、 You can just say どうも (informal, casual way of saying thanks) or どうもありがとうございます。 Don't forget the "う”ｓ　；）

Thank you Risa-san!