Definition:Prime Subfield

The unique minimal subfield in a field $$F$$ is called the prime subfield of $$F$$.

From Field of Characteristic Zero has Unique Prime Subfield, if $$\operatorname{Char} \left({F}\right) = 0$$, then its prime subfield is isomorphic to $$\Q$$, the Field of Rational Numbers.

From Field of Prime Characteristic has Unique Prime Subfield, if $$\operatorname{Char} \left({F}\right) = p$$, then its prime subfield is isomorphic to $$\Z_p$$, the Ring of Integers Modulo $p$.

From Characteristic of Field, $$p$$ is prime.