Question

if a function is neither one-one nor onto , can we say it's a function? if yes , then which function. like this example f:A to B y=f(x)=x^2 +3 A={-1,1,2,3} B={4,5,6,7}
THIS IS NEITHER ONE-ONE NOR ONTO. SO , if it is a function, so what is the name of this ?