You use of to combine two nouns when the first noun identifies the feature of the second noun that you want to talk about.
The average age of the women interviewed was only 21.5.
受访女性的平均年龄只有21.5岁。
the population of this town.
这个城镇的人口。
You use of to combine two nouns, or a noun and a present participle, when the second noun or present participle defines or gives more information about the first noun.
She let out a little cry of pain.
她疼得轻轻叫了一声。
the problem of having a national shortage of teachers.
全国性教师短缺问题。
You use of after nouns referring to actions to specify the person or thing that is affected by the action or that performs the action. For example, 'the kidnapping of the child' refers to an action affecting a child; 'the arrival of the next train' refers to an action performed by a train.
It sets targets for reduction of greenhouse-gas emissions.
它为减少温室气体排放设立了目标。
You use of after words and phrases referring to quantities or groups of things to indicate the substance or thing that is being measured.
dozens of people.
几十人。
a collection of short stories.
一部短篇小说集。
You use of after the name of someone or something to introduce the institution or place they belong to or are connected with.
the governor of Missouri.
密苏里州州长。
You use of after a noun referring to a container to form an expression referring to the container and its contents.
a box of tissues.
一盒纸巾。
a roomful of people.
一屋子人。
You use of after a countable noun and before an uncountable noun when you want to talk about an individual piece or item.
a blade of grass.
…一片草叶。
Marina ate only one slice of bread.
玛丽娜只吃了一片面包。
You use of to indicate the materials or things that form something.
local decorations of wood and straw.
用木头和草制成的本地饰品。
loose-fitting garments of linen.
宽松的亚麻衣服。
You use of after a noun which specifies a particular part of something, to introduce the thing that it is a part of.
the other side of the square.
广场的另一边。
the beginning of the year.
年初。
You use of after some verbs to indicate someone or something else involved in the action.
He'd been dreaming of her.
他一直梦到她。
Listen, I shall be thinking of you always.
听着,我会一直想念你。
You use of after some adjectives to indicate the thing that a feeling or quality relates to.
I have grown very fond of Alec.
我变得很喜欢埃里克。
His father was quite naturally very proud of him.
他父亲很自然地为他感到自豪。
You use of before a word referring to the person who performed an action when saying what you think about the action.
This has been so nice, so terribly kind of you.
你这样实在是太好了。
If something is more of or less of a particular thing, it is that thing to a greater or smaller degree.
Your extra fat may be more of a health risk than you realize.
多余的脂肪对健康的威胁可能比你所意识到的更严重。
You use of to indicate a characteristic or quality that someone or something has.
the worth of their music.
他们音乐的价值。
She is a woman of enviable beauty.
她是个美得让人嫉妒的女人。
You use of to specify an amount, value, or age.
Last Thursday, Nick announced record revenues of $3.4 billion.
上周四,尼克宣布收益达到34亿美元,创下新高。
young people under the age of 16 years.
十六岁以下的年轻人。
You use of after a noun such as 'month' or 'year' to indicate the length of time that some state or activity continues.
eight bruising years of war.
八年艰苦卓绝的战争。