number one
[adjective]
Synonyms: chief, capital, cock, dominant, main, major, outstanding, predominant, preeminent, stellar, excellent, A1, blue-ribbon, first-class, first-rate, first-string, five-star, front-rank, Grade A, superior

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English Thesaurus: main, chief/principal, major, key, number one, ...

[TahlilGaran] English Synonym Dictionary ▲

I. ˌnumber ˈone¹ noun

1. [uncountable] the best, most important, or most successful person or thing in a group:
Until his marriage, his job was number one in his life.
Shearson is number one in the market this year.

2. [uncountable and countable] the musical record that is the most popular at a particular time:
number one in the charts
They’ve had three number ones.

3. look out for number one (also look after number one) spoken to look after yourself and not worry about other people, in a way that may seem selfish

4. [singular, uncountable] spoken informal a word meaning urine, used especially with children to avoid saying this

[TahlilGaran] Dictionary of Contemporary English ▲

II. ˌnumber ˈone² adjective

1. most important or successful in a particular situation:
The University of Maine has the number one hockey team in the country.
Sweden’s number one model

2. first on a list of several things to be considered, done etc:
item number one on the agenda
This has got to be our number one task.

[TahlilGaran] Dictionary of Contemporary English ▲

main larger or more important than all the others:
the main entrance of the building
the main reason for his decision
chief/principal most important. Chief and principal are more formal than main, and are often used in written English:
Coffee is the country’s principal export.
What is the company’s chief objective?
major very important or serious:
Smoking is a major cause of heart disease.
Street crime is becoming a major problem.
key most important, or the one that everything or everyone else depends on:
Education is likely to be a key issue in the election campaign.
Hooper was a key member of the team.
Diet is key.
number one especially spoken most important or best - this phrase sounds a little informal and it is used especially in spoken English:
Reliability is the number one priority.
the number one cause of death
He is still in the number one position.
primary most important - used especially about the most important aim, role, cause, or concern. Primary is more formal than main:
The primary aim of the project was to help students develop their communication skills.
Security is our primary concern.
The primary function of the university was considered to be the teaching of ‘the great cultural disciplines’.
prime very important or most important - used especially about the most important reason, cause, or aim, or about the most likely target or suspect. Prime is more formal than main:
Their prime objective is to increase profits for their shareholders.
Tourists are prime targets for theft and robbery.
core most important - used especially about the things that people should pay most attention to:
the core skills of reading and writing
He wants the company to focus on its core business - advertising.
The party’s core values are individual freedom and reducing the amount of government bureaucracy.
central most important and having more influence than anything else:
The U.S. played a central role in the peace negotiations.
a central theme of the book
The central question is, why are people still so attached to their cars?
predominant most common, typical, or important:
Yellow was the predominant colour everywhere.
High arched windows are a predominant feature in English churches.
New York still has a predominant role in the contemporary art world.

[TahlilGaran] English Thesaurus ▲

number one
[informal]
the most important person, especially when you think this is yourself and you do not care about anyone else.
Half of me thinks I should just look out for number one and not give a damn about anyone else.

[TahlilGaran] English Idioms Dictionary ▲

number one
oneself, one's own interests
He is always looking out for number one and will never do anything for other people.

My friend only thinks about number one and never about anybody else.

[TahlilGaran] English Idioms Dictionary ▲

number one
Number One¹ n. phr., informal Yourself; your own interests; your private or selfish advantage. Usually used in the phrase "look out for number one".
He was well known for his habit of always looking out for number one.
number one² adj. phr.
1. Of first rank or importance; foremost; principal.
He is easily America's number one golfer.
2. Of first grade; of top quality; best.
That is number one western steer beef.

[TahlilGaran] English Idioms Dictionary ▲