【单词背后的故事】 com- 共同， merce- 商业，来自罗马神话中的使者墨丘利（ Mercury ）， 他是商业之神，能给人带来好运和财富，他帮助商人赚钱、盗贼偷钱、骗子骗钱。英语 mercurial 意为“机智，精明的”，就是来源于此，此外， merc- 和 merch- 这两个词根还有表示“商业，交易”的意思。

mercury['mə:kjuri]
a heavy silver-coloured metal which is liquid at ordinary temperatures
a chemical element. Mercury is a poisonous silver liquid metal, used in thermometers.
the smallest planet in the solar system, nearest to the sun
n. 水银；水银柱；【天文学】水星（首字母大写）

mercurial [mə:'kjuəriəl]
lively and quick
changing suddenly and often
intelligent, enthusiastic and quick
often changing or reacting in a way that is unexpected
containing mercury
adj. 水银的；水星的；活泼善变的；多变的，反复无常的 ；敏捷的;精明的
n. 汞剂；水银剂

例句
He is a complicated man-moody, mercurial, with a melancholy streak.
他是一个性格复杂的人—喜怒无常、反复多变、有些忧郁寡欢。
Sometimes he's adultly, and sometimes mercurial, do you konw which is the real him?
他有时老成稳重,有时活泼可爱,你知道哪个才是真实的他么?

commerce ['kɔmə:s] commence
the activities involved in buying and selling things
n. 贸易，商业

短语:
1.active commerce 直接贸易(进出口贸易由本国人办理或由本国船只运输)
2.domestic commerce 国内贸易
3.foreign commerce 对外贸易
4.passive commerce 间接贸易(出口产品由外国船只代运)
5.sea-borne commerce 海上贸易

例句
We must promote commerce with neighbouring countries.
我们必须促进与邻国的贸易。

commercial[kə'mə:ʃəl]
connected with the buying and selling of goods and services
making or intended to make a profit
more concerned with profit and being popular than with quality
paid for by the money charged for broadcasting advertisements
an advertisement on the radio or on television
adj. 商业的；营利的；靠广告收入的
n. 商业广告

耶鲁公开课 - 金融市场课程节选

A commercial bank, like a goldsmith banker, accepts deposits--that's critical and that means you can put money in the bank.

商业银行,就像是一个金匠银行家,接受存款,这一点非常关键,就是说你可以把你的钱放到银行里

mercenary ['mə:sinəri]
interested only in the amount of money that you can get from a situation
a soldier who fights for any country or group that pays them
adj. 雇佣的；唯利是图的
n. 雇佣兵；唯利是图者

耶鲁公开课 - 古希腊历史简介课程节选

There were no kings with the wealth to hire mercenary soldiers.
国王的财富不足以招募雇佣军

merchant ['mə:tʃənt] （ merch 商业 +ant 表示人→商人）
a person whose job is to buy and sell products in large amounts, especially by trading with other countries
n. 商人，批发商；店主
adj. 商业的，商人的

例句
Did you watch Shakespeare's The Merchant of Venice on TV last night?
你昨天晚上在电视上看到莎剧《威尼斯商人》吗?

merchandise ['mə:tʃəndaiz, -dais]
goods that are bought or sold; goods that are for sale in a shop/store
merchandise something to sell something using advertising, etc.
n. 商品；货物
vt. 买卖；推销
vi. 经商

例句
The shop windows are filled with foreign merchandise.
商店橱窗里摆满了外国商品。
If this product is properly merchandised, it should sell very well.
这一产品如果促销得当,该是很畅销的。