The unanimity principle is a Voting Theory principle. Unanimity means "agreement reached by all people".
Using Voting Theory Relations for $N = 2$ we define Unanimity as:
It follows from two principles
If a candidate $a$ is always preferred by the majority to $b$, then we can say that $b$ is dominated by $a$ and never consider $b$ again
The same concept in different disciplines is also often called Dominance