Dial refers to a circular control or display that you turn or point to in order to make something work. The volume knob on a radio is a dial: you rotate it to make the sound louder or softer. Old telephones had rotating dials with holes for your finger, and you'd spin the dial to each number you wanted to call. Combination locks have dials that you turn carefully to the right numbers. Clock faces are also called dials because the hands point to numbers arranged in a circle.

As a verb, to dial means to use one of these controls, especially on a phone. Even though modern phones have buttons or touch screens, we still say “dial a number” out of habit. You might dial your friend's phone number or dial up the heat on a thermostat.

Sometimes people use dial figuratively, as in “dial it back” or “dial down the excitement,” meaning to reduce or moderate something, like turning down the volume on a radio.