Learn Dutch: Neem je de vierde appel? - Do you take the fourth apple?

For most numbers from 2 to 19, you just add -de to the normal number. So vier (four) becomes vierde (fourth). The spelling of the base number usually stays exactly the same.

Why is it Neem je without a -t at the end of the verb?

In a normal statement, it is Je neemt (You take). But there is a special rule for je and jij: when they come right after the verb (like in a question), you drop the -t. So it becomes Neem je?

If the noun was a het word, would vierde change?

No, the ordinal number itself doesn't change, but the article before it does. Ordinal numbers act like adjectives. Since appel is a de word, it's de vierde appel. For a het word, you would say het vierde boek (the fourth book).

Can nemen be used for choosing food, like in English?

Yes! Just like saying 'I'll take the apple' in English, you can use nemen in Dutch when you are picking out food, drinks, or items from a selection.