Inequation is such an ugly, made-up word. Your spell-checker will probably underline it in accusatory red zigzags.
An inequality is a relationship like x < 4 or y ≥ 10. The symbols <, >, ≥ and ≤ are inequality symbols.
So, if we change the equals sign in an equation into an inequality symbol, we get an inequation, like y ≤ 2x + 3.