n.
Function: noun
Date: before 12th century
1 ― see NUMBER table
2 : the number denoting unity
3 a : the first in a set or series ― often used with an attributive noun <day one > b : an article of clothing of a size designated one <wears a one >
4 : a single person or thing <has the one but needs the other>
5 : a one-dollar bill
– at one : at harmony : in a state of agreement
– for one : as one example <I for one disagree>