Definition
First; foremost; best, often used after its headword.
Origins
Piecewise doublet of numero uno.
In Context
- "Commuting to work is the number one reason to own a car."
- "He is my enemy number one."
- "Road safety is a daily tragedy that doesn’t seem to make the front pages even though it’s a number one killer. In some countries, it causes more deaths than small firearms, and in others, more than illnesses."