Learn Dutch: Een kwartier is precies vijftien minuten. - A quarter of an hour is exactly fifteen minutes.

Kwart means "a quarter" (1/4). You use it when reading the clock, like kwart voor acht (quarter to eight). But when you are talking about a duration of 15 minutes ("a quarter of an hour"), Dutch uses the special word kwartier.

Is there a special word like kwartier for "half an hour"?

No, kwartier is a bit of an exception! To say "half an hour", you just combine the regular words for half and hour: een half uur.

Is precies related to the English word "precise"?

Yes, they share the same origin! In Dutch, precies is a very common word used to mean "exactly" or "precisely".

Why does minuten only have one u when the singular word is minuut?

This happens because of Dutch spelling rules. When you add the plural -en to minuut, the syllables divide as mi-nu-ten. Because the u is now at the end of a syllable, it automatically makes a long sound, so the second u is dropped to keep the spelling clean.