1.dark作名词时是不可数名词,表示“傍晚”时,其前不能加冠词。表示“黑暗,无光”时,通常其前加the,作为单数名词跟单数动词连用。
2.in the dark有两种意思,即“在黑暗中”“不知,蒙在鼓里”。

a leap〔shot〕 in the dark
盲目冒险地干,回答等 action, answer, etc. that is risked in the hope that it is correct
It's hard to know exactly what to do—we'll just have to take a shot in the dark.很难说我们怎么办才对——我们只好瞎碰。
Jane's attempt to find her lost ring in the long grass was just a shot in the dark.简试图在草丛中找回她丢失的戒指,那真是一种毫无成功希望的举动。

before〔after〕 dark
在天黑以前〔以后〕before〔after〕 the sun goes down
Try to get home before dark.尽量在天黑以前回家。
He came to my house before dark.他在日暮之前到我家来。
She will get home before dark.她天黑以前将到家。
We still have some way to walk before dark.天黑以前我们还要走一段路。
He arrived after dark.他天黑以后才到达。
Is it safe to walk the streets after dark?天黑以后在街上行走安全吗?
I'm afraid to go out after dark in the city.在城里,我害怕天黑后出门。
I never returned home from the office after dark.我从不在日落后由事务所回家。

in the dark
无知,不知 in a state of ignorance
He kept me in the dark about it.他将此事隐瞒不使我知道。
I am completely in the dark concerning their plans.我对他们的计划一无所知。
We are still in the dark about the cause of the fire.我们还不清楚起火的原因。
I was in the dark about it until she told me.这件事在她告诉我之前,我毫不知情。
We were kept completely in the dark about his plan to sell the company.对他计划将公司出售一事,我们一直蒙在鼓里。

The dark came very early.夜色很早就降临了。
You should turn the light on at dark.黄昏时你应开灯。
They work from dawn till dark.他们从天亮一直工作到天黑。
Some little children are afraid of the dark.有些小孩子怕黑暗。
I made out two dim shapes in the dark.黑暗中我隐约辨出两个模糊的影子。
The blind live in the dark.盲人在黑暗中生活。
They groped in the dark.他们在黑暗中摸索。
I hit my head against the door in the dark.我的头在黑暗中撞到门上去了。
I could see the beam of his flashlight waving around in the dark.我能够看见他的手电筒光在黑暗中四下晃动。
She struggled in the dark, without advice, without encouragement.她在黑暗中挣扎,无人指教,无人鼓励。
There is too much dark in this painting.这画颜色太暗。

dark, darkness
这两个词都有“黑暗”的意思。其区别是:
1.dark多指经常的状况; darkness指一时的状况。例如:
The old man enjoys sitting in the dark.这位老人喜欢坐在暗处。
For a time, they kept silent, sitting in the darkness.他们一段时间坐在暗处,一言不发。
2.表示“傍晚”时,只能用dark,不能用darkness。例如:
The city looks more beautiful at dark.傍晚时分,这个城市显得更加美丽。
3.in the dark表示“不知,蒙在鼓里”时,不能用darkness。

［同义词］ adj. black, cloudy, darkling, dim, evil, gloomy, grim, ignorant, infamous, joyless, lightless, obscure, shadowy, shady, wicked
［反义词］ adj. bright, cheerful, happy, light
［词源］ ＜古英语dearc(藏,黑暗)

1.dark的基本意思是“黑暗的”,指缺乏使人能够看见或识别自己面前物体的必要照明(自然的或人工的),可指缺乏表现愉快心情的光泽或缺少道德或精神上的光辉。dark有时还用来修饰颜色,指颜色不鲜明、不明亮。
2.dark在句中可用作定语、表语或宾语补足语。
3.dark的比较级为darker,最高级为darkest。

dark horse
黑马(有本事而深藏不露的人) person who hides special personal qualities or abilities
“A dark horse” is one that shows unexpected racing speed and comes in first, even though the experts said he had little chance of winning.一匹已被专家认为没有获胜希望的马,却在赛马中跑出了出人意料的速度,夺得了第一名,这就叫“黑马”。
He's a bit of a dark horse: he was earning a fortune, but nobody knew.他可算是藏龙卧虎:赚大钱,但没人知道。
Don't think you'll beat him easily, he may be a dark horse.不要以为你会轻而易举地胜过他,他可能是出人意料的高手。

keep dark
保守秘密 keep as a secret; conceal

▲keep sth dark
He kept his political activities dark.他对他的政治活动保守秘密。
I'll keep it dark about it as possible.对那件事我尽可能保密。
He keeps his plans dark.他对他的计划秘而不宣。

用作定语
▲～+n.
 That was a dark, moonless night.那是一个黑暗的,无月光的夜晚。
The long dark night passed by.漫长的黑夜过去了。
The darkest hour is before the dawn.黎明前是最黑暗的时刻。
A dark cloud is a sign of rain.乌云是降雨的信号。
You seem in a dark temper.你似乎很不高兴。
There is some dark meaning in his words.他的话里有某种隐晦的含义。
The war was a dark period for us.这场战争对我们来说是个黑暗时期。
用作表语
▲S+be+～
 It is dark.天黑了。
When I got up at five that cold morning, it was pitch dark.在那个寒冷的早晨我5点钟起身时,天一片漆黑。
It was not quite dark as yet.天还没有完全黑下来。
It was nearly dark when we came home.我们到家时天已快黑了。
It was getting dark when they arrived at the farm.他们到达农场时,天已渐渐黑下来了。
It's so dark here in the garden I think you'd better lead the way.花园里这么黑,我想你最好在前面带路。
Outside the forest, it was not so dark.森林外面没有那么阴暗。
The colour of this cloth is too dark.这布的颜色太深了。
The prospects look dark.前景看起来不佳。
▲S+be+～+prep.-phrase
 The building is dark with soot and smoke.烟尘使那幢建筑物变黑了。
It is as dark as pitch.天暗得漆黑一团。
He was always quite dark about that matter.他对那件事情总是缄口不言。
His face was dark with anger.他气得脸色发青。
▲S+be+～+to-v
 The night is too dark for us to see.夜色太暗,我们看不见。
It's getting too dark to take photographs.天色渐晚,不能照相。
▲S+be+～+(that/)wh-clause
 So dark are the shadows that a man standing there could not be seen.阴影很暗,人站在里面不会被看见。

dark, dim
dark与dim都有“黑暗”的意思,其区别是:dark的意思是“黑暗的”,指黑暗无光,而dim的意思是“灰暗的”,表示由于光照不足所造成的昏暗状态,刚好达到看不清或分辨不清物体。修饰光线、灯光、阳光等只能用dim。例如:
With only the fire burning, the room was dim.只有火炉在燃烧,房里光线很暗。
He was reading a magazine under the dim light of a candle.他在微弱的烛光下看杂志。

形容词dark有时也可受名词修饰,如pitch dark night意为“漆黑的夜晚”。