number one含义和用法比较多，请看：
1. 名词，头号人物（组织或事物）；最重要的人（或事物）；最好的人（或事物）；老大；第一，首位：
The university is ranked number one in the country for engineering.
在工程学领域上，这所大学位居本国第一。
We're number one in the used car business.
在二手车交易中我们是老大。
They believe that it's not enough to be number one in the world.
他们认为仅仅成为世界第一是不够的。
One thing has stayed at number one, though: he wants to visit a movie set.
不过,有一件事一直排在第一位：他想参观电影片场。
2.自己
Looking after number one is all she thinks about.
她一心只顾着自己。《牛津高阶英汉双解词典》
My priority is to look after number one — to create a lifestyle I am happy with.
我首先要顾好自己，追求自己喜欢的生活方式。
3. 名词（不可数名词, 可数名词）周销售量最高的流行歌曲（或唱片）；排行榜冠军
She's had three number ones.
她已有三张唱片曾经名列周销售量排行榜榜首。
Paula is the only artist to achieve four number ones from a debut album.
葆拉是唯一的首张唱片4次荣登排行榜榜首的艺人。
The new album went straight to number one.
这张新的歌曲专辑一举登上了周销售量榜首。
The band's last single shot straight to number one in the charts.
乐队的最新单曲唱片在每周排行榜上一路飙升至首位。
Their album has occupied the Number One slot for the past six weeks.
他们的唱片在最近六周占据排行榜首位。
The bands are constantly jockeying with each other for the number one spot.
这些乐队经常相互耍手段以谋取榜首位置。
4.撒尿（尤作为儿童用语）
It's only a number one.
只撒了尿。头号的;头等的;最重要的
5. 形容词，头号的;头等的;最重要的；排名第一的；最铁（牢靠）的，
The economy is the number one issue by far.
到目前为止，经济是头等大事。
Lack of money is our number one difficulty.
缺钱是我们最大的困难。
Accidents are still the number one cause of premature death for Americans
交通事故仍然是造成美国人过早死亡的头号因素。
I've been one of your number one fans for nigh on three years now
我一直是你的铁杆粉丝之一，到现在快3年了。
But the number one thing on her list is to see her favorite band in concert.
但她清单上的第一件事是在音乐会上看到她最喜欢的乐队。
Thinking hard about it, I came to realize that my team might not be the number one team in Georgia, but they were depending on me ．
仔细想了想，我开始意识到我的队伍也许不是乔治亚州最棒的，但他们十分依赖我。
Williams has confirmed his position as the world's number one snooker player.
威廉姆斯巩固了自己世界头号斯诺克选手的地位。
Finally, we faced the number one team in the state ．
最后,我们对阵的是这个州排名第一的球队。
6.一号的……，一路的……
There's a Number One bus every three minutes.
一路公共汽车每隔3分钟就有一班。