radical

Favoring fundamental change, or change at the root cause of a matter.

His beliefs are radical.

Pertaining to a root (of a plant).

Pertaining to the basic or intrinsic nature of something.

The most determined exertions of that authority, against them, only showed their radical independence.

Thoroughgoing; far-reaching.

The spread of the cancer required radical surgery, and the entire organ was removed.

Phoenix and Lubbock are both caught in severe drought, and it is going to get much worse. We may see many such [dust] storms in the decades ahead, along with species extinctions, radical disturbance of ecosystems, and intensified social conflict over land and water. Welcome to the Anthropocene, the epoch when humans have become a major geological and climatic force.

Of or pertaining to the root of a word.

A member of the most progressive wing of the Liberal Party; someone favouring social reform (but generally stopping short of socialism).

A member of an influential, centrist political party favouring moderate social reform, a republican constitution, and secular politics.

A person with radical opinions.

A root (of a number or quantity).

In logographic writing systems such as the Chinese writing system, the portion of a character (if any) that provides an indication of its meaning, as opposed to phonetic.

The boy recognised the Chinese characters, though the calligraphy looked a bit strange, as if drawn by someone who had seen them and copied them out radical by radical without knowing what they meant.