Questions & Answers about Tarvitsen haarukan, koska syön kalaa.
Why is the word for fork written as haarukan instead of haarukka?
It is the object of the verb tarvitsen (I need). Since you need one whole, countable fork, it takes the total object case, which looks like the genitive and ends in -n. Also, notice the consonant gradation: the double kk in haarukka weakens to a single k when the ending is added.
Why is kalaa in the partitive case while haarukan ends in -n?
The verb syödä (to eat) takes the partitive case here because eating is an ongoing, incomplete action. Furthermore, kala (fish) is being treated as an uncountable mass noun (some fish) rather than one whole, specific fish. Since you need a complete, countable fork, haarukan gets the -n ending.
Would I ever use the partitive case with tarvita and say tarvitsen haarukkaa?
Not when you need a single, countable object. The verb tarvita (to need) strongly prefers a total object. However, you must use the partitive if the sentence is negative, like en tarvitse haarukkaa (I do not need a fork), or if you need an uncountable substance, like tarvitsen vettä (I need water).
Does the word koska affect the word order of the second clause?