1. The first element in a countable series
   "She finished number one in her class";
   - first, number 1
    
2. The first or highest in an ordering or series
   "She was number one in her class";
   - first
    
3. A reference to yourself or myself etc.; 'take care of number one' means to put your own interests first
   "In this competitive industry, you have to look out for number one"

Derived forms: number ones

Type of: no., ordinal, ordinal number, rank, self

Encyclopedia: Number one