Learn Finnish: Kova myrsky saapui yhtäkkiä. - The strong storm arrived suddenly.

The basic verb is saapua (to arrive), a Type 1 verb. Its stem is saapu-. To form the past tense for a stem ending in -u, we simply attach the past marker -i to get saapui. The -u stays right where it is!

Why isn't there a personal ending on saapui like -n or -t?

Because the subject is myrsky (the storm), which is a third-person singular subject (it). In the past tense, third-person singular verbs do not get an extra personal ending; they just end with the past marker -i.

The word kova usually means "hard". Why is it translated as "strong" here?

In Finnish, kova is a very versatile adjective. While it means "hard" for physical objects, it is also the standard word used for intense weather (like wind or storms), loud noises, and high speeds.

Does yhtäkkiä come from the number one (yksi)?

Yes! It is a compound word built from yhtä (a form of yksi, meaning one) and äkkiä (suddenly or quickly). Together, they translate to "all of a sudden" or "suddenly".