number_one
1. [ noun ] (informal) a reference to yourself or myself etc.
Examples:

"take care of number one" means to put your own interests first

Related terms: self colloquialism
2. [ noun ] the first or highest in an ordering or series
Synonyms: first
Examples:

: "He wanted to be the first"

Related terms: rank former
3. [ noun ] (mathematics) the first element in a countable series
Synonyms: first number_1
Examples:

"the first of the month"

Related terms: ordinal_number
Similar spelling:   number_1
  numberless
  number_system
  numbers
  numberplate
  numbers_pool
  numbers_game
  numbering