Question

there is a sale on today.为什么是a sale on，此时sale可数么，

there is a sale on today.为什么是a sale on，此时sale可数么，不是on sale么

Answer 1

仍然是不可数名词，但是不可数名词加a ,这叫抽象名词具体化
不可数的抽象名词用来表示可数的人或物，在特殊情况下，有些抽象名词可以进行具体化，即名词的数和词义发生了变化。
attraction beauty comfort danger death delight experience failure help honor joy kindness pity pleasure satisfaction shame success surprise trouble wonder worry sight knowledge room atmosphere fortune
1. attraction (U)吸引,吸引力; ©有吸引力的人或事物.
到月球上旅行的想法对我没有什么吸引力.
The idea of traveling to the moon has little attraction for me.
城里明亮的灯,戏院,电影等有巨大的吸引力.
The city's bright lights, theatres, and movies are great attractions.
这份工作最吸引人的是薪水高.
One of the main attractions of the job is the high salary.
2. beauty 美,美丽;美丽的人或事物
She was a famous beauty in her youth.
她年轻时是个有名的美人.
That new car is an absolute beauty.
那辆新车漂亮极了.

3. comfort 安慰,慰藉,宽恕;令人感到安慰的人或事物
The news brought comfort to all of us.
这消息给我们大家带来了安慰.
His husband was a great comfort to her when she was ill.
她生病时,她丈夫对她是个极大的安慰.
4. danger 危险,风险; 危险的人,危险因素
Children's lives are in danger every time they cross this road.
孩子们每次过这条马路都面临着生命危险.
out of danger 脱离危险
警方说这个男子对公众是个危险分子.
Police said the man was a danger to the public.
How does nature form a danger to people in the world.
自然现象是如何对全球人类造成威胁的。

5. death死,死亡;死亡的人
Air pollution alone causes about three million deaths every year.
仅空气污染就造成了每年近三百万人死亡.
If the hurricane had happened during the daytime, there would have been many more deaths.
若飓风发生在白天,那么死亡的人会多的多.

6. delight 高兴,愉快,快乐;令人高兴的事,乐事,乐趣
To our great delight, the day turned out fine.
我们感到高兴的是天气转晴了.
The guitar is a delight to play.
弹吉他是件很惬意的事.
Her singing is a delight.
她的歌声使人快乐.

7. difficulty困难,艰难,难度,困难性;难做,难懂,难应付的事,难事,难点,难题
She got the door open with difficulty.
她艰难地把门打开了.
I had the great difficulty in persuading her.
我为了说服她,费了好大的劲儿.
He wants to marry her, but his parents are making difficulties.
他想娶她,但他父母从中阻挠.
她在旅行时遇到了许多伤脑筋的事.
She met with many difficulties when traveling.

8. experience经验;经历,体验
Do you have any previous experience of this kind of work?
你以前做过这种工作吗?
Valuable experience 宝贵的经验
He hand many interesting experiences while traveling in Africa.

9. failure 失败; 失败的人湖事物
The success or failure of the plan depends on you.
这项计划的成败取决于你.
Failure in one examination should not stop you trying again.
一次考试不及格不应该防碍你再试一次.
整个事情彻底失败了.
The whole thing was a complete failure.
She was a failure as a teacher.
她当教师并不成功.

10. help 帮助;有帮助的人或事物
A tape-recorder or a mp3 is a great help for you to learn English.
录音机或mp3对你学英语帮助很大.
我在家里是妈妈的好帮手.
I am a good help to my mother at home.

11. honour 荣幸,荣誉;给某人/某事增光的人或事物
我们为祖国的荣誉而战.
We fought for the honour of our country.
参加这次大会我感到很荣幸.
It is a great honour for me to be present at the conference.

Answer 2

on 是在进行的意思，既不与前面的sale 搭配也与后面的today无关
There is a sale today可以表示今天有特价销售，加上的这个 on是想表达在今天有特价销售在进行，on在这里是副词，“进行”的意思，不是介词“在”的意思

Answer 3

sale on是词组 他俩组合才是名次

Answer 4

on是today的…
on sale一般是什么东西on sale

追问

那sale前为什么加a，可数么

还有为什么要在today前加on,there is a sale today很好啊

追答

a sale就是大减价 特卖的意思

追问

那后面那个问题呢

追答

你说的也没错

on today强调今天

有 就今天 的意思