In mathematics, a radical expression is defined as any expression containing a radical (√) symbol - includes square roots, cube roots and so forth. Expressing in simplest radical form just means simplifying a radical so that there are no more square roots, cube roots, 4th roots, etc left to find.
So √12 is in radical form. I think what you are asking for is to reduce the expression to its simplest radical form.
So 12 = 4*3, √12 = √4 * √3.
We can ‘reduce’ this by noting that √4 =2, so the expression becomes 2√3.
This cannot be further reduced because 3 isn’t a square or divisible by a square, so 2√3 is the simplest radical form.
