Learn Icelandic: Bollinn datt en maðurinn greip hann. - The cup fell but the man caught it.

Detta is a strong verb. Instead of adding a typical past tense ending, strong verbs change their inner vowel to show that they are in the past tense. For the singular past tense of detta, the vowel changes to a, making it datt.

Is greip another strong verb? What is its infinitive form?

Yes! Greip is the singular past tense of grípa (to catch or grab). It follows a very common pattern for strong verbs: if the infinitive has an í, the singular past tense often changes it to an ei. You will see this same pattern in words like bíta (to bite) becoming beit.

Why does the sentence use hann for it instead of það?

In Icelandic, pronouns must match the grammatical gender of the noun they are replacing, even for inanimate objects. Because the word for cup (bolli) is a masculine noun, we must use the masculine pronoun hann to mean it.

Since the cup is the object being caught, shouldn't hann be in the accusative case?

It is! For the masculine pronoun hann, the nominative (subject) case and the accusative (object) case happen to be exactly the same. The word only changes form if it needs to be in the dative case (honum) or the genitive case (hans).