I. ˈra-di-kəl adjective
Etymology: Middle English, from Late Latin radicalis, from Latin radic-, radix root — more at root
Date: 14th century
1. : of, relating to, or proceeding from a root: as
a.
(1) : of or growing from the root of a plant
radical tubers
(2) : growing from the base of a stem, from a rootlike stem, or from a stem that does not rise above the ground
radical leaves
b. : of, relating to, or constituting a linguistic root
c. : of or relating to a mathematical root
d. : designed to remove the root of a disease or all diseased and potentially diseased tissue
radical surgery
radical mastectomy
2. : of or relating to the origin : fundamental
3.
a. : marked by a considerable departure from the usual or traditional : extreme
b. : tending or disposed to make extreme changes in existing views, habits, conditions, or institutions
c. : of, relating to, or constituting a political group associated with views, practices, and policies of extreme change
d. : advocating extreme measures to retain or restore a political state of affairs
the radical right
4. slang : excellent , cool
• rad·i·cal·ness noun
II. noun
Date: 1641
1.
a. : a root part
b. : a basic principle : foundation
2.
a. : root 6
b. : a sound or letter belonging to a radical
3. : one who is radical
4. : free radical ; also : a group of atoms bonded together that is considered an entity in various kinds of reactions or as a subunit of a larger molecule
5.
a. : a mathematical expression indicating a root by means of a radical sign
b. : radical sign