Learn Finnish: Laiva on ylittänyt valtameren nopeasti. - The ship has crossed the ocean quickly.

The perfect tense in Finnish is built using the verb olla (to be) as a helper verb, followed by the past participle of the main verb. In this sentence, on is in the third-person singular to match the subject laiva (the ship), and ylittänyt is the past participle of the verb ylittää (to cross).

Why does the past participle ylittänyt end in -nyt?

The ending -nyt is used to form the active past participle for singular subjects. Because laiva is just one ship, we use the singular ending. If the sentence were about multiple ships, the plural ending -neet would be used instead: Laivat ovat ylittäneet...

Why is the word for ocean written as valtameren instead of its basic form, valtameri?

Valtameren is the direct object of the sentence. Because the perfect tense here describes a fully completed action in an affirmative sentence (the ship has crossed it completely), the object takes the genitive-like -n ending. If the crossing was still ongoing, or if the sentence was negative, it would use the partitive case (valtamerta).

How do we get the word nopeasti (quickly)?