Operand
An operand is an argument for an operator. It applies to any of the operand: to differentiate them further, they are named with their position: first, second, etc., or their name.
<?php
// One operand
$b = !$a;
// two operands
$a = 1 + 3;
// Three operands
$c = $a ? 2 : 4;
?>