Questions & Answers about Hún reið heim á hestinum.
Reið is the past tense, 3rd person singular form of the verb ríða, which means to ride.
So:
- ríða = to ride
- hún ríður = she rides / she is riding
- hún reið = she rode
This is a strong verb, so the past tense is formed by a vowel change rather than by adding a regular ending.
Because heim already means homeward / to home. It is an adverb of direction.
This works a lot like English go home, where English also does not need to:
- fara heim = go home
- koma heim = come home
- ríða heim = ride home
So in Hún reið heim, the word heim already includes the idea of movement toward home.