Cyclotomic integers

Let $𝜁 𝑛 = e 2 𝑖 𝜋 / 𝑛$ be a primitive $𝑛$ th root of unity. Then the cyclotomic integers $ℤ [𝜁 𝑛]$ are the ring of integers in the Cyclotomic field $ℚ [𝜁 𝑛]$ . ring