numberone
nounUK /ˌnʌmbə ˈwʌn/
US /ˌnʌmbər ˈwʌn/
The person or thing that is the very best or comes first.
She is the number one player on our team.
OTHER MEANINGS
2. The number 1.
Write the number one at the top of the page.
3. The most important person or thing to someone.
My family is my number one.
4. The act of urinating, used especially with children.
The toddler said he needed to go number one.