Learn Finnish: Paikallinen opas auttoi meitä.

Auttaa is a Type 1 verb. To form the past tense, we usually add an -i-. However, for two-syllable verbs ending in -aa (like auttaa, antaa, or maksaa), that final -a turns into an -o- before the past tense -i. Since this sentence is in the third-person singular ("the guide helped"), there is no personal ending added to the end, leaving us with auttoi.

Why does auttoi have a strong double -tt-? Doesn't the past tense usually trigger consonant gradation?

Consonant gradation (changing -tt- to -t-) happens when we add a personal ending that "closes" the syllable, like -n for "I" or -t for "you". Because the third-person past tense doesn't take a personal ending, the syllable stays open and the stem remains strong. If you wanted to say "I helped", it would weaken to autoin.

Why is the word for "us" in the partitive case (meitä)?

The verb auttaa (to help) is what we call a "partitive verb". This means it always requires the object of the sentence to be in the partitive case, regardless of whether the action was completed or not. Therefore, "us" must be translated to the partitive meitä instead of the basic form me.

How is the adjective paikallinen (local) formed?