Hey! Cool that you're learning Finnish :) Consonant gradation in Finnish is quite tricky and has a loooooot of exceptions and different categories based on how words are converted. I tried to figure out how to explain it to you but didn't really get anywhere with that but the basic rule is that if the word has a geminate (basically a double consonant), like 'matto', it will turn into a short consonant, 'maton'. Then you have to add a suffix so it'd actually make sense in a sentence, in this case '-n'. If the word has a shirt vowel, 'mato', the vowel will disappear or change forms, 'madon'. All the changing forms are exceptions so you'll just have to learn them by heart. The difference between the suffixes in 'kouluun, koulussa, koulusta' and 'koululle, koululla, koululta' are a bit easier :p As you probably know the stem word is 'koulu', school, and the suffixes '-un', '-ssa', '-sta', '-lle', '-lla', '-lta' are all place markers. They also express direction. kouluun = to school koulussa = in school koulusta = from school koululle = to school koululla = at school koululta = from school The first three are used to really emphasize where you're at, like when you're literally inside the school and having class or something, the other three are used when you're either in the school or close to the school and you're just kinda chilling there or passing by. The difference between saying 'Menen kouluun' (I'm going to school) and 'Menen koululle' is that in the first one you're actually going to attend class and in the second one you're just going to the school building and you don't really want to tell anyone what you're actually going to do there. So I guess the second one could be translated 'I'm going to THE school', you know what I'm saying? It's pretty much the same deal with using the other suffixes, the first ones just imply that you're in school for a reason, like to attend class and the other ones that you're there for something else, or that you're just passing by or something. Hope this helps this you a little :)