The mathematical sign for less than is <. This sign is used in inequalities, which are statements indicating one number or expression is larger or smaller than another. The less than sign with a horizontal line drawn just below it means "less than or equal to."
An example using the less than sign is 5 < 10. Several signs show the relationship between expressions in a mathematical statement. The equal sign is =, and the "not equal sign" is the same as an equal sign with a left-slanting line through it. The greater than sign is >, and the greater than or equal to sign is > with a horizontal line beneath it.