<p><strong>Adjective:</strong></p><ul><li>Of or going to the root or origin; fundamental: There is a radical difference between the two interpretations of the sacred text, one justifying war and the other requiring nonviolent resistance.</li><li>Extreme, especially as regards change from accepted or traditional forms: A radical change in the policy of the company.</li><li>Favoring drastic political, economic, or social reforms: Radical ideas; radical and anarchistic ideologues.</li><li>Favoring, supporting, or representing extreme forms of religious fundamentalism: Radical fundamentalists and their rejection of modern science.</li><li>Forming a basis or foundation: What is the radical reason for his choice?</li><li>Existing inherently in a thing or person: Radical defects of character.</li><li>Characterized by a marked departure from prevailing methods, practices, or ideas, particularly in the arts; experimental; unorthodox: The composer’s radical approach to sound, using timbre and rhythm rather than pitch, was declared “noise” by an influential critic.</li><li>Slang: Excellent; wonderful; cool; rad: You got here on an electric skateboard? That's radical!</li><li>Mathematics: Pertaining to or forming a root; denoting or pertaining to the radical sign.</li><li>Grammar: Of or pertaining to the root of a word.</li><li>Botany: Of or arising from the root or the base of the stem.</li></ul><p><strong>Noun:</strong></p><ul><li>A person who holds or follows strong convictions or extreme principles; extremist.</li><li>A person who advocates fundamental political, economic, and social reforms by direct and often uncompromising methods.</li><li>Mathematics: A quantity expressed as a root of another quantity.</li><li>The set of elements of a ring, some power of which is contained in a given ideal.</li><li>Radical sign (def).</li><li>Chemistry: Group (def).</li><li>Free radical (def).</li><li>Grammar: Root 1 (def).</li><li>(In Chinese writing) One of 214 ideographic elements used in combination with phonetics to form thousands of different characters.</li></ul>