Learn Icelandic: Þar inni eru tíu vélar. - In there are ten machines.

Vélar is the plural form of the feminine noun vél (machine). Adding -ar to the end of the word is one of the most common ways to make feminine nouns plural in the nominative case.

Why does the verb eru (are) come before tíu vélar (ten machines)?

Icelandic strictly follows the verb-second or V2 rule, meaning the main verb must be the second idea in a standard sentence. Because this sentence starts with the location phrase Þar inni (In there), the verb eru has to come right after it, pushing the subject tíu vélar after the verb.

Does Þar inni literally mean "In there"?

Yes, exactly! Þar means "there" and inni means "inside" or "in". When you put them together as Þar inni, it means "in there" or "inside there".

Do I need to change the ending of the number tíu to match the feminine plural noun?

No, you don't. In Icelandic, only the numbers 1 through 4 change their form to match the gender and case of the noun they are describing. The number tíu (ten) and all numbers from 5 upwards stay exactly the same regardless of what they are counting.