number one; item 1
Used as a label for the first in a numbered series, such as a building, room, document, or list item.
The meeting will be held in Room 1.
Please check item 1 of the document.
public enemy No. 1
Standard kanji spelling.
Numerical form, common in addresses, lists, and technical contexts.
Compound of 一 (いち, 'one') and 号 (ごう, 'number').