1 number one noun
or No. 1
or No. 1
Learner's definition of NUMBER ONE
[noncount]
1
a : a person, thing, or position that is highest in rank : the most important person or thing in a group of people or things头号人物；头等重要的事物 -
Who's number one in this office?谁是这个办公室的头儿？
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Getting the car fixed is number one on my list of priorities.在我非做不可的事情当中，修车是头等大事。
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I'll tell you why we can't go on a vacation: number one, we can't afford it, and number two, we'll miss my sister's party.我告诉你为什么我们不能去度假：首先，我们负担不起；其次，我们会错过我姐姐的派对。
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Two of their songs have gone to number one [=the highest rank] on the pop charts.他们的两首歌曲上了流行音乐排行榜的榜首。
b : the most successful person or thing in a group of people or things佼佼者；最成功的人（或事物） -
Her movie is currently number one at the box office.她的电影目前票房第一。
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When the goal was scored, the fans started to chant, “We're number one, we're number one.”进球得分后，球迷们开始反复呼喊：“我们最棒，我们最棒。”
2
: your own happiness, health, or success : yourself自己 -
I've been taking care of other people for too long. It's time for me to take care of number one.我照顾别人太久了，到了该考虑自己的时候了。
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If you don't look out for number one [=if you don't take care of yourself], who will?如果你不照顾自己，谁会照顾你？
3
informal : liquid waste from the body : urine —
used mainly by children or when speaking to children撒尿（主要用于儿童语言或与儿童的对话） — compare number two 2 number one adjective
or No. 1
or No. 1
Learner's definition of NUMBER ONE
: highest in rank or importance头号的；头等的 -
Heart disease is the country's number one [=leading] killer of women.心脏病是这个国家女性的头号杀手。
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My number one [=main] concern is getting my car fixed.我的头等大事是修车。
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The book is the company's number one seller.这本书是公司最畅销的书。
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Rule number one is don't get caught!最主要的就是不要被抓住！
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He's public enemy number one: the nation's most wanted criminal.他是头号公敌：这个国家的头号通缉犯。