Questions & Answers about Báðir fæturnir eru mjög kaldir.
Why do we use báðir here instead of another form of the word for both?
Báðir is the masculine nominative plural form. It has to match the gender, number, and case of the noun it describes. Since the word for foot (fótur) is a masculine noun and is the subject of the sentence, we use báðir.
Why is it fæturnir (the feet) instead of just fætur (feet) like in English?
In Icelandic, the word for both requires the noun to have the definite article attached to it. While English says both feet, Icelandic literally says both the feet (báðir fæturnir).
I know the word for foot is fótur. Why does it change to fætur here?
Fótur is an irregular noun that changes its root vowel in the plural form. The vowel ó changes to æ, making it fætur. Then we add the masculine plural definite article -nir to the end, giving us fæturnir.
Why does the word for cold end in -ir (kaldir)?
Adjectives in Icelandic must match the noun they describe in gender, number, and case. Because fæturnir is masculine, plural, and in the nominative case, the adjective kaldur (cold) must take the matching masculine plural ending -ir, becoming kaldir.