radical
//ˈrædɪkəl//
Adjective
relating to or affecting the fundamental nature of something; far-reaching or thorough
The company needs to make radical changes to survive.
advocating or based on thorough or complete political or social change; representing or supporting an extreme or progressive section of a political party
The party proposed radical reforms to the education system.
of or relating to the root of something; fundamental
We need to make radical changes to the system.
Antonym
Noun
a person who advocates thorough or complete political or social reform; a member of a political party or section of a party pursuing extreme policies
The radicals in the party demanded immediate and sweeping changes to the system.
a group of atoms behaving as a unit in a number of compounds (chemistry)
A hydroxyl radical consists of one oxygen atom and one hydrogen atom.
the root or base form of a word (linguistics)
In linguistics, the radical of 'running' is 'run'.