Additive function
= Additive function
An additive function on an <additive semigroup> satisfies $f(x+y)=f(x)+f(y)$ whenever $x$, $y$, and $x+y$ belong to its domain.
= Additive function
An additive function on an <additive semigroup> satisfies $f(x+y)=f(x)+f(y)$ whenever $x$, $y$, and $x+y$ belong to its domain.