0 the number 1 -- （数字）1
1 a member of a group of people or things -- （一群人或事物）中的一个，之一
EMI is one of the world's largest record companies. EMI公司是世界最大的唱片公司之一。
Finding a cure for cancer is one of the biggest challenges facing medical researchers. 寻找治疗癌症的方法是医学研究者面临的最大挑战之一。
Our organization is just one of many charities that are providing famine relief in the region. 我们的组织只是给这个地区提供饥荒救济的众多慈善组织中的一个。
2 used to refer to a time in the future that is not yet decided -- （用于指将来某个未确定的时间）某一
3 used to refer to a particular occasion while avoiding stating the exact moment -- 某一天；某一刻；某一次
4 a single thing; not two or more -- 单独一个；一个
Eat them one at a time (= separately). 一次吃一个。
I think we should paint the bedroom all one (= in a single) colour. 我觉得我们应该把卧室刷成一种颜色。
UK Do you think five of us will manage to squeeze into the one car? 你觉得我们5个人能够挤进一辆车里吗？
With this model you get a radio, CD player, and MP3 dock all in one. 这种型号的产品将收音机、CD播放机和MP3播放器接口集于一体。
5 used when saying there is no other person or thing -- 唯一的一个
6 used before the name of someone who is not known -- （用于不认识的人的名字前）某一个
Her solicitor is one John Wintersgill. 她的律师是个名叫约翰‧温特斯吉尔的人。
8 used to refer to a particular thing or person within a group or range of things or people that are possible or available -- （一群人或一批东西中的）一个
I have a few books on Chinese food. You can borrow one if you want. 我买了几本关于中国菜的书，如果你喜欢可以借一本。
Which one would you like? 你想要哪一个？
Please make a copy for everybody in the office and a few extra ones for the visitors. 请你给办公室里每人印一份，再多印几份给来访者。
"Which cake would you like?" "The one in the front." “你想要哪个蛋糕？”“前面的那个。”
French croissants are so much better than the ones we get here. 法国羊角面包比我们这里的好吃得多。
There were lots of people watching, and not one of them offered to help. 站着旁观的有许多人，却没有一个人主动帮忙。
I've received no replies to my job applications - not a single one (= none). 我的求职申请没有任何回复——一个都没有。
Chris is the one (= the person) with curly brown hair. 克里斯就是那个长着褐色卷发的人。
I'm not one to criticize other people, as you know. 你知道，我这人从来不批评人。
I've never been one for staying out late. 我从不喜欢在外呆到很晚。
9 used to talk about one person or thing compared with other similar or related people or things -- （表示与另一类似或相关的人或物���对照的）一个
They look so similar it's often difficult to distinguish one from the other. 它们看上去这么相似，常常很难区分开来。
You may have one or the other, but not both. 这个和那个你可以选一个，但不能都要。
Crime and freedom are inseparable. You can't have one without the other. 犯罪和自由如影随形，不可能只取其一。
10 any person, but not a particular person -- 任何人；一个人
One has an obligation to one's friends. 一个人对他的朋友是负有责任的。
Trouble broke out in the match when one of the players called a member of the other team a cheat.
He can't tell one wine from another, so don't give him any of the expensive stuff.
