This is the 145th most frequent Icelandic word.
nýju
The Icelandic word "nýju" means "new" in the dative plural form.
Here, "nýju" is used as an adjective in the accusative singular definite form to describe the feminine noun "bókina" (the book), indicating 'the new book'.
Ég keypti nýju bókina í gær.
I bought the new book yesterday.
Here, "nýju" is again an adjective, this time in the accusative plural definite form, describing the neuter noun "hlutina" (the things) as 'the new things'.
Hann er ekki að tala um nýju hlutina.
He is not talking about the new things.
In this sentence, "nýju" appears as an adjective in the accusative plural definite form modifying the masculine noun "kennarana" (the teachers), meaning 'the new teachers'.