Radical form refers to the expression of a number or algebraic expression in terms of roots, such as square roots, cube roots, or nth roots. The symbol √ is used to denote a root of a number and is called a radical. The number written before the radical is called the index or degree, and the number under the radical is called the radicand. The simplest radical form means the radical form of a number or algebraic expression in simplest terms, where there are no more square roots, cube roots, 4th roots, etc left to find.

To express a radical in simplest form, we need to follow some rules. For example, we can simplify a radical by finding the highest square number that divides into the radicand evenly and expressing it as the product of the square root of that number and the remaining factor. We can also simplify radicals by using laws of radicals, such as the nth root of a positive number to the power n equals the number itself.

In summary, radical form refers to the expression of a number or algebraic expression in terms of roots, and simplest radical form means the radical form of a number or algebraic expression in simplest terms. To express a radical in simplest form, we need to follow some rules, such as finding the highest square number that divides into the radicand evenly and using laws of radicals.