common

将“common”与“commun”相连，想象“commun”代表社区或公共（community），而“-on”是“common”的词尾，共同的意思。这样就可以记忆为“common”表示普遍的、常见的。

common 普通，公共

com-, 强调。-mon, 公共，词源同mean, communicate.

common

common: [13] Common comes ultimately from an Indo-European base *moi-, *mei-, signifying ‘change, exchange’, which also produced English immune, mutate, mutual, and remunerate. A derivative of this base, *moin-, *mein- seems to have joined up with the Indo- European collective *kom- to produce *komoin-, *komein- ‘shared by all’.

In Germanic this became *gamainiz, source of English mean ‘despicable’, while in Latin it gave commūnis, source, via Old French comun, of English common. Both the Latin and French forms have given English a number of derivatives: from the former we have community [14] (Latin commūnitātis), communion [14] (Latin commūniō), and communicate [16] (Latin commūnicāre), while the latter has yielded commune [13] (Old French comuner) and communism [19] (French communisme, coined around 1840).
=> communicate, communism, community, immune, mean, mutual, mutate, remunerate

common (adj.)

c. 1300, "belonging to all, general," from Old French comun "common, general, free, open, public" (9c., Modern French commun), from Latin communis "in common, public, shared by all or many; general, not specific; familiar, not pretentious," from PIE *ko-moin-i- "held in common," compound adjective formed from *ko- "together" + *moi-n-, suffixed form of root *mei- (1) "change, exchange" (see mutable), hence literally "shared by all."

Second element of the compound also is the source of Latin munia "duties, public duties, functions," those related to munia "office." Perhaps reinforced in Old French by the Germanic form of PIE *ko-moin-i- (compare Old English gemæne "common, public, general, universal;" see mean (adj.)), which came to French via Frankish.

Used disparagingly of women and criminals since c. 1300. Common pleas is 13c., from Anglo-French communs plets, hearing civil actions by one subject against another as opposed to pleas of the crown. Common prayer is contrasted with private prayer. Common stock is attested from 1888.

common (n.)

late 15c., "land held in common," from common (adj.). Commons "the third estate of the English people as represented in Parliament," is from late 14c. Latin communis also served as a noun meaning "common property, state, commonwealth."

1. His destination was Chobham Common, a long way from his Cotswold home.

他的目的地是乔伯姆公地，那里和他在科茨沃尔德的家离得很远。

2. Eczema is a common skin complaint which often runs in families.

湿疹是一种常见的皮肤病，通常具遗传性。

3. Canadian libel law is based on English common law.

加拿大的诽谤法是以英国的习惯法为基础的。

4. The crew are of different nation-alities and have no common language.

船员来自不同国家，语言不通。

5. His name was Hansen, a common name in Norway.

他的名字叫汉森，在挪威是一个常见的名字。

【usual, common, universal, general, average】
这组词都有“普通”的意思，其区别是：
usual: a.通常的，惯常的，强调"习惯性的，符合规章制度的"，是个一般用语。
common: a.常见的，普通的，不足为奇的，有时引申为"平凡的"，强调事物的共同性。另外，它还有"公共的，共同的"之意。
• Car accidents are a common occurrence. 交通事故是很普通的事件。
universal: a.普遍的，比general语气更强，有"全然没有例外"的意思。
• Poverty is a universal problem all over the world. 贫困是世界各地普遍存在的问题。
general: a.普通的，一般的，表示涉及到各方面，强调整体性而非个别和例外，该词的反义词为particular。
• In general, the economy is doing well now. 总的来说，现在的经济形式还不错。
average: a.普通的，一般的，它强调的是一般水准或普通水准；通常在有数字出现的情况下，表示"平均的"。
• The average runner can run 2 miles in fifteen minutes. 跑步者15分钟内平均跑两英里。

【typical, unique, rare, common, particular, special】
typical: 典型的
unique: 唯一的
rare: 罕见的，珍贵的
common: 共同的
particular: 特定的，特殊的
special: 特殊的，特别的

【reciprocal, joint, mutual, common】
这组词都有“共同的，相互的”的意思，其区别是：
reciprocal: 着重互惠，有来有往。
joint: 强调至少两人或两方共同占用，侧重指一个统一体。
mutual: 着重彼此共有或共享，局限于双方的关系。
common: 侧重两人或多人共有共同，但不暗示彼此间存在的等价关系。

【usual, ordinary, common, popular, normal, universal, general】
usual: 平常的，惯常的
ordinary: 平凡的，词义与common接近，指符合一般或常规事物标准或相同的规格，因而只具有普通的特性
common: 普通的，共有的，指从质量或品德上无特殊或显眼之处，属于大多数人或事物所具有的，常见的；
popular: 大众的，受欢迎的，指属于或代表大众的某事物，强调常见的，大众化的特征
normal: 正常的，正规的，指符合某种标准的
universal: 普遍的，有完全没有例外之意；
general: 一般的，普通的，含有例外情况较少之意或暗示包括全部同一范畴的事物；

【usual, ordinary, common, popular, universal, commonplace, general】
这组词都有“普通的，普遍的”的意思，其区别是：
usual: 指常见常闻和常做的事或举动，强调惯常性。
ordinary: 用于物，指每天发生，十分平淡无奇；用于人，指无特别之处，很一般。
common: 多用于指物，侧重很常见，不稀奇。
popular: 指适应大众爱好、需要，为大家所公认或接受。
universal: 与general同义，但语气较强，侧重对每个人或事物都适用，根本没有例外。
commonplace: 强调缺少新意。
general: 语气强于common，侧重大多如此，很少有例外情况。