Questions & Answers about Jakkinn er hans, en úrið er hennar.
Do hans and hennar change to match the gender of the jacket and the watch?
Do hans and hennar mean 'his/hers' or 'his/her'?
They mean both! English uses different words depending on the sentence structure (her watch vs. the watch is hers). Icelandic keeps it simple: hennar covers both 'her' and 'hers', and hans covers both versions of 'his'.
Why do the words for jacket and watch end in -inn and -ið?
These endings are the Icelandic equivalent of the English word 'the'. Instead of a separate word, Icelandic attaches 'the' to the end of the noun. The masculine word jakki becomes jakkinn (the jacket), and the neuter word úr becomes úrið (the watch).
What if I wanted to say 'his jacket' instead of 'the jacket is his'?
To say 'his jacket', you still use the 'the' form of the noun and put the pronoun right after it: jakkinn hans. This literally translates to 'the jacket his', which is the standard way to show ownership in Icelandic.