This is the 359th most frequent Icelandic word.
haustið
"Haustið" means "the autumn" or "the fall" in English.
Here, the word 'haustið' refers to the autumn season in Icelandic, indicated by the definite article suffix -ið.
Haustið er uppáhalds árstíð mín.
Autumn is my favorite season.
In this sentence, 'haustinu' is the dative case of 'haustið', as prepositions like 'í' ('in') require the dative case in Icelandic.
Ég elska litina í haustinu.
I love the colors in the autumn.
Here, 'haustin' is used in the plural form, which denotes multiple autumn seasons, showing a variation in usage of the word.