Questions & Answers about Poika rikkoo ikkunan vasaralla.
How does vasaralla mean "with a hammer" without a separate word for "with"?
The ending -lla is the Adessive case. While it often means "on top of", its other main job is to show the instrument, tool, or means used to do an action. Adding -lla to vasara (hammer) expresses "by means of a hammer" or "with a hammer".
Why is the object ikkunan and not ikkuna or the partitive ikkunaa?
The verb rikkoa (to break) here describes a completed action that affects the entire window. This requires the total object form, which takes the accusative ending -n. If the boy were only trying to break it without succeeding, or if it was an ongoing action, you would use the partitive form ikkunaa.
Why doesn't the double kk in rikkoo drop to a single k through consonant gradation?
The dictionary form is rikkoa (to break). The third-person singular adds a lengthened vowel to make hän rikkoo. Because the syllable ends in a vowel (an open syllable), the double -kk- stays in its strong grade. You only see the weak grade single -k- when an ending closes the syllable with a consonant, such as in minä rikon (I break).
Does the instrument vasaralla always have to go at the very end of the sentence?
In neutral Finnish word order, the instrument usually goes at the end. You could say Vasaralla poika rikkoo ikkunan, but putting the tool first shifts the emphasis, making it sound like "It is with a hammer that the boy breaks the window."