Learn Croatian: Osamnaest gostiju čeka. - Eighteen guests are waiting.

In Croatian, when you use a number from five onwards, the verb that follows must be in the third-person singular. Even though there are multiple guests, the grammar treats the quantity as a single unit, so we use čeka (waits) instead of the plural čekaju (they wait).

Why is the word for guests gostiju instead of the regular plural gosti?

This is the main rule for numbers five and above: they require the noun that follows them to be in the genitive plural case. The noun gost (guest) is a bit special because its genitive plural takes the ending -iju, making it gostiju.

Do I ever need to change the ending of the number osamnaest?

No. Numbers from five onwards are invariable, meaning they never change their form regardless of the gender or case of the noun they describe. It is always osamnaest.

How would this sentence look if there were only four guests?

Numbers two, three, and four use a different rule: the noun takes the genitive singular and the verb is plural. So, four guests are waiting would be Četiri gosta čekaju. Notice how both the noun and the verb change when the number drops below five!