Questions & Answers about Þetta eru ekki fjórir kettir.
Why does the sentence use Þetta eru if þetta means "this"?
In Icelandic, when you use þetta to point something out or introduce it ("This is..." or "These are..."), it stays in the fixed neuter singular form þetta, even if the things you are pointing at are plural. However, the verb must match the plural noun that follows, which is why we use eru (are) instead of er (is).
Why is the number four written as fjórir?
In Icelandic, the numbers 1 through 4 change their endings to match the gender of the noun they count. Because kettir (cats) is a masculine word, we use the masculine form of four, which is fjórir. If we were counting feminine nouns, it would be fjórar.
What is the singular form of kettir, and why does the vowel change?
The singular form is köttur (a cat). When masculine words become plural, the vowels inside the word often change. Here, the ö shifts to an e, making the plural kettir.
Where does the negative word ekki go in a sentence like this?
In standard Icelandic sentences, ekki (not) generally comes directly after the main verb. Here it follows eru (are).