radical

(especially of change or action) relating to or affecting the fundamental nature of something; far-reaching or thorough.

advocating or based on thorough or complete political or social change; representing or supporting an extreme or progressive section of a political party.

denoting or relating to the roots of a word.

relating to or forming the root of a number or quantity.

of, or springing direct from, the root or stem base of a plant.

very good; excellent.

a person who advocates thorough or complete political or social change, or a member of a political party or section of a party pursuing such aims.

a group of atoms behaving as a unit in a number of compounds.

the root or base form of a word.

a quantity forming or expressed as the root of another.