Onto
A function is onto if for every \(y\), there is an \(x\) such that \(f(x) = y\).
For each \(b \in B\) there exists at least one \(a \in A\) such that \(f(a) = b\).
Translation: Every element of \(B\) is "pointed to"
A function is onto if for every \(y\), there is an \(x\) such that \(f(x) = y\).
For each \(b \in B\) there exists at least one \(a \in A\) such that \(f(a) = b\).
Translation: Every element of \(B\) is "pointed to"