Learn Icelandic: Hundurinn hleypur til afa.

The preposition til is used to show movement towards a destination, like a person or a place. Crucially, whenever you use til, the noun that follows it must change into the genitive case.

Why is the word for grandpa afa instead of afi?

Because it comes right after the preposition til. Til always forces the following noun into the genitive case. For masculine nouns that end in -i in their base form, like afi, the genitive form changes the ending to -a, making it afa.

How does the word hundurinn mean 'the dog'?

In Icelandic, the word 'the' is usually added to the end of the noun as a suffix rather than being a separate word before it. The base word for dog is hundur, and adding the masculine suffix -inn makes it hundurinn (the dog).

The dictionary form of the verb 'to run' is hlaupa. Why is it spelled hleypur here?

Many common Icelandic verbs change their core vowels in the present tense. For the verb hlaupa, the vowel combination au changes to ey when it is paired with singular subjects like 'the dog' (which acts as a third-person 'he/she/it' subject).