Breakdown of Minä en ymmärrä vaikeaa sanaa.
minä
I
sana
word
ei
no / not (negative verb)
vaikea
difficult / hard
Questions & Answers about Minä en ymmärrä vaikeaa sanaa.
Why are vaikeaa and sanaa in the partitive case?
There are actually two reasons here! First, the verb ymmärtää (to understand) is a partitive verb, meaning it always takes a partitive object. Second, this is a negative sentence (en ymmärrä). In Finnish, the object of a negative sentence must always be in the partitive case anyway.
Why does the adjective vaikea get an extra -a at the end?
In Finnish, adjectives must match the grammatical case of the noun they describe. Because the noun sana (word) is in the partitive case (sanaa), the adjective vaikea (difficult) must also take the partitive ending, becoming vaikeaa.
Where did the -t- go in the verb ymmärtää?
It changed because of a spelling rule called consonant gradation. To make a negative sentence, you use the negative verb plus the verb stem. You find the stem by taking the I form (ymmärrän) and dropping the -n. The strong -rt- in the dictionary form ymmärtää softens into a weak -rr- in ymmärrä.
Do I always have to use the word Minä here?
No, you can simply say En ymmärrä vaikeaa sanaa. The negative verb en already means I do not, so the pronoun Minä is optional and is mostly used when you want to add a little extra emphasis to the fact that it is YOU who does not understand.