Questions & Answers about Vatnið eyðileggur húsið.
Because both nouns are neuter singular definite forms.
In Icelandic, the definite article is usually attached to the end of the noun instead of being a separate word. So:
- vatn → vatnið
- hús → húsið
Here, both nouns are in forms where neuter singular definite happens to look like -ið.
The dictionary forms are:
- vatn = the base form of vatnið
- eyðileggja = the infinitive/base form of eyðileggur
- hús = the base form of húsið
So the sentence uses:
- a definite form of vatn
- the present-tense form of eyðileggja
- a definite form of hús