Questions & Answers about Älä revi vanhaa kirjaa.
Why is the verb form revi instead of the dictionary form repiä?
In a negative command, we use älä plus the connegative stem of the verb. To find this stem for repiä (to tear, verb type 1), take the minä (I) form, which is revin, and drop the -n. This leaves us with revi.
Why does repiä change its 'p' to a 'v' in revi?
This is consonant gradation. Verb type 1 verbs often undergo consonant gradation when you make the minä form. The strong p in repiä weakens to a v in revin. Since the negative imperative uses that exact same stem, the weak v is used in älä revi.
Why are the words vanhaa and kirjaa in the partitive case?
In Finnish, if a sentence is negative, the object almost always has to be in the partitive case. Because älä makes this a negative command, the object (the old book) becomes vanhaa kirjaa instead of the basic form vanha kirja.
If I wanted to tell someone TO tear the book, would it still be vanhaa kirjaa?