wood—woods, water—waters, sand—sands

　　7.定冠词加姓氏的复数表示一家人。 the Turners,

　　the Smiths, the Wangs.

　　8.集体名词people, police, cattle 总是作复数，

　　( people 作民族，种族时有单复数两种形式)

　　Many cattle are kept.

　　Several police were on duty.

　　The Chinese are a brave and hard-working people.

　　The English are a funny people.

　　9.集体名词class, public, family, population, team, crew, committee 等单复数都有，但意义不同。

　　The class is big.---- The class are taking notes in English.

　　The population in China is larger.---- 80% of the population

　　in China are peasants.

　　10. hair， fruit 通常作单数，表示总体。

　　His hair is grey. a rich harvest of fruit

　　如果表示若干根头发，表示种类的水果时，可以加复数词尾。

　　He had a few white hairs.

　　What fruits are on sale in this season ?

　　11.以s 结尾的学科名词只作单数。mathematics , physics, politics, 等。(news)

　　12.glasses， trousers， scissors， shoes， spectacles，等常用复数;但如果这些词前用 a pair of …// this pair of…//that pair of…等修饰时谓语动词有pair 来决定。

　　Where are my glasses ?

　　My new pair of trousers is too long.

　　Here are some new pairs of shoes.

　　13.不可数名词没有复数形式，如果表示“一个”的概念，可用单位词。

　　a piece of news / information / advice / bread / cake / paper / meat / coal…

　　a bottle of ink, a grain of rice , a cake of soap…