Breakdown of Nemandinn finnur ekki tannkremið sitt.
nemandinn
the student
ekki
not
finna
to find
sinn
his/her/their own (sinn, sína, sitt)
Questions & Answers about Nemandinn finnur ekki tannkremið sitt.
Why does the sentence use sitt for 'his' instead of hans?
Sitt is the reflexive possessive pronoun meaning 'his own'. Because the student is looking for his own toothpaste, we use a form of sinn. If we used hans, it would mean he could not find another guy's toothpaste!
How do we choose the exact form sitt here?
The reflexive pronoun must match the gender, number, and case of the thing being owned, not the owner. Tannkrem (toothpaste) is a neuter word. It is in the accusative case here because it is the direct object of the verb finnur (finds). The neuter, accusative, singular form of sinn is sitt.
Why does tannkrem have the definite article suffix -ið if the pronoun sitt is right next to it?
In English, we just say 'his toothpaste'. But in Icelandic, it is standard to keep the definite article on the noun when it is followed by a possessive pronoun. You are literally saying 'the toothpaste his' (tannkremið sitt).
The dictionary word for student is nemandi. How does it become nemandinn?
Nemandi is a masculine word. Since the student is doing the action, the word is in the nominative case. To say 'the student', you just add the definite article suffix -nn to the end of the base word.