What does radical mean?
A radical is most commonly a person who seeks fundamental change in a political, social, or religious institution. The adjective can mean either thoroughly transformative, as in “radical reform,” or associated with radical politics. In other fields, the word has specialized meanings: in chemistry, it denotes a molecule or atom with an unpaired electron; in mathematics, it indicates a root; and in biology, it refers to a plant’s root or its fundamental structural part. The word comes from Latin radix, meaning “root,” and its history reflects the idea of reaching down to the root of a matter rather than making superficial adjustments. Because “radical” can suggest either serious reform or political extremity, context often determines whether its tone is approving, neutral, or critical.
A person who supports or advocates fundamental or extreme change, especially in politics.
"The movement attracted young radicals from across the country."
The term can be used approvingly or critically, depending on the speaker and political context.
Characterized by or favoring fundamental or sweeping change.
"The committee proposed a radical redesign of the curriculum."
In political contexts, it may imply a position more extreme than moderate reform.
In chemistry, a chemical species with one or more unpaired electrons; in mathematics, a symbol or expression indicating a root.
"The reaction begins when a free radical attacks the substrate."
The root of a plant, or the fundamental part from which something develops.
"The seedling sends a slender radicle down into the soil."
The plural is used for people who advocate fundamental change and for chemical or mathematical radicals.
"Several radicals joined the protest, calling for a complete reform of the system."
From the Latin radix, meaning “root,” the word radical grew from its literal roots to describe ideas that seek to get to the root of a problem.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does radical come from?
The word comes through Old French from Latin radicalis, meaning “of or pertaining to a root” and derived from radix, “root.” In the 14th century it was used in the botanical sense for a plant root, and it later acquired senses connected with fundamental or original principles. By the late 18th century, its political sense had developed for people seeking sweeping institutional change.
Related word forms
How radical is actually used
In political contexts, “radical” can be neutral and indicate support for fundamental reform, or strongly critical, suggesting extreme or revolutionary views. In chemistry and mathematics, it is standard technical terminology.
Easily confused with radical
A radicand is the number or expression whose square root is being taken, whereas a radical is the root symbol or the root itself.
A radicle is the embryonic root of a germinating plant, while the root-related sense of radical refers more generally to a root or fundamental constituent.