A
function [math]f : A \href{/cs2800/wiki/index.php/%5Cto}{\to} B
[/math] is
injective if,
for all [math]x_1
[/math] and
[math]x_2 \href{/cs2800/wiki/index.php/%5Cin}{\in} A
[/math],
whenever [math]f(x_1) = f(x_2)
[/math], we have
[math]x_1 = x_2
[/math].
