the other
Definitions
The remaining one of two or more distinct items or people.
A person or group viewed as fundamentally different or alien from oneself or one's own social group.
The alternative or second option in a set of two.
Examples
I have two cats; one is black and the other is white.
She held a book in one hand and a coffee cup in the other.
Synonyms
the alternative the remaining one the second option the counterpart the different one