adj.(形容词)

1. 必要的，必须的，必需的，不可缺少的，有必要，需要
2. 必然的，无法避免的，不可避免的，必定的，不得已的，事出无奈
3. 强迫的
4. 应该
5. 一定

n.(名词)

1. （生活）必需品，必要的物品
2. 厕所
3. 钱，收入，必需的金钱（与the连用）

adj.(形容词)

1. 必要的,必需的 essential for a purpose; that cannot be done without or avoided
2. 必然的,不可避免的 that must be; inevitable

Noun:

1. anything indispensable;

   "food and shelter are necessities of life"
   "the essentials of the good life"
   "allow farmers to buy their requirements under favorable conditions"
   "a place where the requisites of water fuel and fodder can be obtained"
   

Adjective:

1. absolutely essential

2. unavoidably determined by prior circumstances;

   "the necessary consequences of one's actions"
   

1. 必需的：注:*有限应用(limited applicability),**适宜的(suitable),***有重要价值(important),****必需的(necessary)损伤等级(AIS) 为使肌体损伤程度达到量化,美国机动交通医学会(1990)制定了损伤分级标准,如表2所示.

2. 必须的：二、花费是常见的(ordinary)和必须的(necessary). 「常见的」定义是,其花费在行业内、商业上很平常,被业者广泛接受. 「必须的」的定义是该花费对生意很有帮助. 这里的关键因素是旅行的主要目的是商业,其中穿插几天游玩也可视为常见的.

3. 必需品：2、 商品满足需要的属性:奢侈品(luxury)的需求,对价格是有弹性的,而必需品(necessary)是缺乏弹性的.

用作定语～+ n.

1. My money came short of the necessary sum.
   我的钱不足所需的数目。
2. Do you have the necessary skills for this job?
   你具备做这项工作所必需的技能吗?
3. They joined the wires and made the necessary new connection.
   他们把电线接了起来,接通了所需的新线路。
4. I'll leave it to you make the necessary arrangements.
   我将让你作出必要的安排。
5. The lawyers will draw up all the necessary papers.
   律师们将拟定出所有必要的文件。
6. No one foresees how the necessary restriction of the population will be effected.
   任何人都无法预知将如何实现对人口的必要限制。
7. They will meet in Beijing to debate taking necessary actions against environmental pollution.
   他们将在北京会晤并讨论采取必要措施防止环境污染。

用作表语S+be+～

1. A year's guarantee on the television set for all repairs might be necessary.
   必须为电视机提供为期一年免费修理的保单。
2. A climber must learn to discriminate as to when compass bearings are necessary and when they are not.
   一个登山者必须学会辨别什么时候需要罗盘测定方位,什么时候不需要。
3. Under certain conditions, answering back sarcastically is necessary.
   在某种情况下,反唇相讥是必要的。

S+be+～+ prep .-phrase

1. Patience and understanding are necessary for a teacher of infants.
   耐心和理解是幼儿教师必不可少的。
2. What is necessary for one person is not always necessary for another.
   对某人来说是必需的东西,对别人则未必如此。
3. These reference books are necessary to scientists.
   这些参考书是科学工作者所必需的。
4. Sleep is necessary to one's health.
   睡眠对健康是必要的。

It is/was+～+(for sb) to- v

1. It was necessary to jump on the ice coated mounds of brush several times before they could flush.
   你得在这些被冰覆盖的树丛上跳上好几下,才能把它们惊起。
2. It's necessary to raise wages on the basis of increasing production.
   需要在增加生产的基础上增加工资。
3. Because the company was doing more business, it was necessary to expand the factory.
   由于公司业务的扩大,扩大工厂是必然的。
4. It was necessary to retire several generals who lacked energy and enterprise.
   使几位缺乏精力和上进心的将军解职是必要的。
5. It is sometimes necessary to indulge a sick child.
   迁就一个生病的小孩有时是必要的。
6. It is both important and necessary to note this difference.
   注意到这个差别是重要的和必要的。
7. Is it really necessary for me to attend the meeting?
   我真的必须出席会议吗?
8. It's necessary for us to net the currant bushes.
   我们有必要用网盖上红醋栗树。
9. It is necessary for them to decide on which type of fuel is most suitable.
   他们必须决定哪一种燃料最合适。

It is/was+～+that-clause

1. It is necessary that everyone be there in time.
   大家都按时到达那里是必要的。
2. It's necessary that young and old people should communicate more with each other.
   年轻人和老年人有必要保持更多的联系。

用作宾语补足语S+V+O+～

1. We consider it necessary that the machine should be oiled regularly.
   我们认为机器必须定期加油。
2. This has made it necessary for agriculture and industry to develop very quickly.
   这就使得工农业必须飞速发展。
3. I felt it necessary to speak about our shortcomings.
   我觉得有必要谈谈我们的缺点。
4. Some students hold it necessary to be able to speak English.
   有些学生认为能讲英语是非常必要的。

其他

1. The National People's Congress holds one session each year. When necessary, the session may be advanced or postponed.
   全国人民代表大会每年召开一次会议,必要时,会期可以提前或推迟。
2. If necessary, the heavy machinery can be brought into action.
   若有必要,可以使用重型机械。
3. If necessary,I'll go there again.
   如有必要,我会再去那里的。

a necessary evil

不得不认可的不合意甚至有害的事物 thing that is undesirable and possibly harmful but must be accepted for practical reasons

• Pincher..left the ship with..a little bundle of necessaries.

  出自：Taffrail

She will make necessary arrangements.

她会作好必要的准备。

If necessary, please warehouse the goods.

如有必要，请将该货存入仓库。

The necessary outcome of a war is a fall in production.

战争带来的必然结果就是生产力下降。

It may be necessary to buy a new one.

也许有必要买个新的了。

It doesn't seem necessary for us to meet.

我们似乎没必要见面。

Only use your car when absolutely necessary.

非用不可的时候再用你的汽车。

If necessary , you can contact me at home.

必要的话，我在家时你也可以和我联系。

I'll make the necessary arrangements.

我会做一些必要的安排。

This is a necessary consequence of progress.

这是发展的必然后果。

I kept the engine running because it might be necessary to leave fast...

我没让发动机熄火，因为也许需要迅速离开。

We will do whatever is necessary to stop them...

我们要采取一切必要措施去阻止他们。

Wastage was no doubt a necessary consequence of war...

巨大的损耗无疑是战争的必然结果。

Scientific work is differentiated from art by its necessary connection with the idea of progress.

科学工作与艺术的区别在于它与人类进步有着必然联系。

...a small parcel of necessaries tied up in a handkerchief and carried on a stick.

用手绢包好挑在棍子上的一小包生活必需品

If necessary, the airship can stay up there for days to keep out of danger...

必要时，飞艇能在那里停留数天以躲避危险。

The army needs men who are willing to fight, when necessary...

军队需要在必要时愿意投入战斗的军人。

They were ready to die , if necessary, for their country.

必要时, 他们愿为国捐躯.

This place is rather cramped.

这地方太局促了.

They always sum up their ( work ) experience whenever it is necessary, so they improve rapidly.

他们总是随时总结经验, 所以工作质量提高很快.

He wasn't good navigator, so it is necessary that the coastline remain in sight as he moved from one harbor to the next.

他不擅航海, 所以当他从一码头驶到另一码头时,得一直沿海岸线航行.

He believed that in building socialism it was necessary to make thorough plans on behalf of the state.

他认为搞社会主义,要替国家好好打算盘.

It's necessary for leading cadres to keep frequent contacts with the masses.

领导应和群众经常见面.

It's necessary for us to net the currant bushes.

我们有必要用网盖上红醋栗树.

They has possessed themselves of all the necessary material.

他们已取得了所有必要的材料.

It is both important and necessary to note this difference.

注意到这个差距是重要的和必要的.

The ability to do this will be necessary in future flights to distant planets.

将来飞往遥远的行星时,需要这样的能力.

This has made it necessary for agriculture and industry to develop very quickly.

这就使得工农业必须飞速发展.

Is it necessary to send a car for them?

用得着派车去接他们 吗 ?

adj.(形容词)

necessary, essential, needful, requisite

这组词都有“必要的”“必需的”意思。其区别是：

1.necessary为常用词,多指总体上长期而言的需要; needful常指近期或眼下所需; essential含有缺少某一因素便不能运转、生存的意思; requisite常指某一具体任务中所需的具体东西,否则就会影响任务的完成。例如:

The were the instruments needful for his work.那是他工作所需要的工具。

We can live without clothes, but food and drink are essential to life.没有衣服我们可以生存,但是食物和水是维持生命所必不可少的。

Past experience is requisite for the job.过去的经验是做这工作的必要条件。

2.语气上, essential比necessary强; requisite是正式用语。

3.necessary和essential用在主语从句中时要用“(should+) v. ”。

indispensable，essential，necessary，requisite

这些形容词均有“必不可少的、必需的”之意。

indispensable语气强，侧重指绝对必要性或不可缺少性。

essential指对事物本身性质具有决定性的重要性，暗含不可缺少，否则便无法存在。

necessary最常用词，侧重由客观因素决定的某种需要，强调不可避免，但并非绝不可缺少。

requisite正式用词，特指为实现某一目的或得到某种结果而应有的需要，有时可与necessary换用。

adj.(形容词)

我必须在7点以前完成作业。

误 I am necessary to finish my homework before seven o'clock.

正 It is necessary for me to finish my homework before seven o'clock.

析 表示“某人必须做某事”时,须用It is necessary for sb to- v 结构。

• ☆ 14世纪中期进入英语，直接源自古典拉丁语的necessarius；最初源自古典拉丁语的necesse，意为不可避免的，不可缺少的。