radical

radical 根本的，激进的

rad-,根，-ical,形容词后缀。即根上的，引申词义根本的，激进的。

radical

radical: [14] Etymologically, radical means ‘of roots’. Its modern political meaning, based on the metaphor of fundamental change, going to the ‘roots’ of things, did not begin to emerge until the 18th century. The word was borrowed from late Latin rādīcālis, a derivative of Latin rādīx ‘root’ (source of English radish [OE] and probably related to root).
=> radish, ramify, root

radical (adj.)

late 14c., in a medieval philosophical sense, from Late Latin radicalis "of or having roots," from Latin radix (genitive radicis) "root" (see radish). Meaning "going to the origin, essential" is from 1650s. Radical sign in mathematics is from 1680s.

Political sense of "reformist" (via notion of "change from the roots") is first recorded 1802 (n.), 1817 (adj.), of the extreme section of the British Liberal party (radical reform had been a current phrase since 1786); meaning "unconventional" is from 1921. U.S. youth slang use is from 1983, from 1970s surfer slang meaning "at the limits of control." Radical chic is attested from 1970; popularized, if not coined, by Tom Wolfe. Radical empiricism coined 1897 by William James (see empiricism).

radical (n.)

1630s, "root part of a word, from radical (adj.) Political sense from 1802; chemical sense from 1816.

1. There will be a radical swing to the right or the left.

这样将出现极左或极右的情况。

2. Radical feminism is currently the fashionable topic among the chattering classes.

激进的女权主义是时下名嘴阶层热议的话题。

3. This thesis led to a radical reshaping of Labour policies.

这篇论文导致了工党政策的彻底改变。

4. He remained for some years avowedly radical in his political outlook.

他多年来保持公然激进的政治观。

5. The Conservative government will not slacken the pace of radical reform.

保守党政府不会放慢激进改革的步伐。

【vital, essential, basic, fundamental, radical】
这组词都有“基本的，基础的”的意思，其区别是：
vital: 正式用词，侧重指维持生命、活力必不可少的，或生死攸关的。
essential: 语气比basic和fundamental强，强调必不可少，暗含某物如缺少某部分，则失去本质特征的意味。
basic: 普通用词，指明确、具体的基础或起点。
fundamental: 书面用词，不如basic使用广泛，侧重指作为基础、根本的抽象的事物。
radical: 着重指事物的根本或其来源。