Define the set of integers

To describe a temperature of 2 degrees above zero, a balance of $50, or 600 feet above sea level, we can use numbers called (1). All (2) are (3) than 0, and we can write them with or without a (4) sign.

To describe a temperature of 2 degrees below zero, $50 overdrawn, or 600 feet below sea level, we need to use (1). All (2) are (3) than 0, and they are written using a (4) sign.