Learn Turkish: Bir çeyrek on beş dakikadır. - A quarter is fifteen minutes.

In Turkish, when you use a number before a noun (like on beş for fifteen), the noun stays in its singular form. So it is always on beş dakika, never on beş dakikalar.

What does the -dır suffix do at the end of dakikadır?

The -dır suffix is a formal way to say "is" or "are". It is often used to state general facts, definitions, or objective truths in Turkish. Here, it establishes the mathematical fact that a quarter is fifteen minutes.

Does çeyrek only refer to time?

No, çeyrek simply means a mathematical quarter (one fourth). While it is heavily used for telling time, you will also see it used for food, money, or measurements, such as çeyrek ekmek (a quarter of a loaf of bread).

Why do we use bir before çeyrek here, but not when reading the time?

In this sentence, we are defining what "a quarter" (one single quarter) is, so we use bir to mean "a". When telling the time (like saying a quarter past the hour), the word çeyrek acts as a fixed time phrase and the bir is dropped.