radical

basic, essential, fundamental, radical, vital

名词 radical:

1. (chemistry) two or more atoms bound together as a single unit and forming part of a molecule
   同义词：group, chemical group
2. an atom or group of atoms with at least one unpaired electron; in the body it is usually an oxygen molecule than has lost an electron and will stabilize itself by stealing an electron from a nearby molecule
   同义词：free radical
3. a person who has radical ideas or opinions
4. a character conveying the lexical meaning of a logogram
5. a sign placed in front of an expression to denote that a root is to be extracted
   同义词：radical sign
6. (linguistics) the form of a word after all affixes are removed
   同义词：root, root word, base, stem, theme

形容词 radical:

1. (used of opinions and actions) far beyond the norm
   同义词：extremist, ultra
2. markedly new or introducing radical change
   同义词：revolutionary
3. arising from or going to the root
4. of or relating to or constituting a linguistic root
5. especially of leaves; located at the base of a plant or stem; especially arising directly from the root or rootstock or a root-like stem
   同义词：basal

1. I don't belong to the school of thought that favours radical change.
   我不属於激进派。
2. Radical political views.
   激进的政治观点
3. Ted is a fire-eating radical.
   泰德是个咄咄逼人的急进份子。
4. They called for a radical reform of our tax system.
   他们要求对税收制度进行根本改革。
5. The talks are aimed at radical reductions in the level of weapons.
   那些会谈都以大幅度裁减军备为目标。

rad.i.cal

adj.（形容词）
Arising from or going to a root or source; basic:
根本的，根源的：产生于或到达根部或源泉的；基础的：
例句：
a radical flaw in a plan; chose the radical solution of starting all over again.
计划的根本性缺陷；选择重新开始的根本解决方法

Departing markedly from the usual or customary; extreme:
极端的，彻底的：明显背离常规或习惯的；极端的：
例句：
radical opinions on education.
对教育的极端的见解

Favoring or effecting fundamental or revolutionary changes in current practices, conditions, or institutions:
激进的，改革的：支持或引起目前的惯例、条件或制度根本性或革命性的变化的：
例句：
radical political views.
激进的政治观点

Linguistics Of or being a root:
【语言学】 词根的：属于或作为词根的：
例句：
a radical form.
词根形式

Botany Arising from the root or its crown:
【植物学】 根生的，根的：生于根部或冠部的：
例句：
radical leaves.
根生的叶

n.（名词）
One who advocates fundamental or revolutionary changes in current practices, conditions, or institutions:
激进分子：在目前的习惯、条件或制度下鼓动根本性或革命性改变的人：
例句：
radicals seeking to overthrow the social order.
企图扰乱社会次序的激进分子

Abbr. rad.Mathematics The root of a quantity as indicated by the radical sign.
缩写 rad.【数学】 根，根号：用根号表示出来的一个数的根
Symbol R An atom or a group of atoms with at least one unpaired electron.
符号 R 原子因，基团：至少有一个游离电子的原子或一组原子
Abbr. rad.Linguistics See root
缩写 rad.【语言学】 参见 root

来源：
Middle English [of a root]
中古英语 [根]
from Late Latin r3doc3lis [having roots]
源自 后期拉丁语 r3doc3lis [有根的]
from Latin r3dox r3doc- [root] * see wr3d-
源自 拉丁语 r3dox r3doc- [根] *参见 wr3d-

【引伸】
rad.ically
adv.（副词）
rad.icalness
n.（名词）