Main Entry: ¹rad·i·cal

Pronunciation: \ˈra-di-kəl\

Function: 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