At first I thought the definite Man would be Manen because I didn't realize that you need to add an extra "n" when making Man definite. Is there a rule to doubling consonants like "n" when making a word definite or is it simply something that you have to learn for the words that do it?
The thing is that we often don’t write n and m double when they’re at the end of words. This is a silly thing but we’ll have to deal with it. We write han, hon, man, kan, tom, glöm! but we pronounce them as if they were written hann, honn, mann, kann, tomm, glömm. However, when you add further vowels to the word, then you typically write them double again (but not always): mannen, kunna, tomma, glömma. So you could say the invisible n resurfaces again in the definite form.