A Greek combining form used in words meaning dry: "The Greek element xero- is used with several words referring to dry, dryness."

"One example of a word using xero- is xerosis which refers to a dryness, as of the skin, eyes, or mucous membranes."

1. The numeral or symbol 0, indicating the absence of quantity: "If 100 is subtracted from 100, it will obviously equal zero."
2. Nothing at all: "The medical researchers are striving to reduce the mortality rate to zero."
3. The point from which the graduation figures of a scale begins: "On the Celsius scale, zero (0°), is the temperature of melting ice, equivalent to 32° on the Fahrenheit scale."
4. A person who is not important, interesting, popular, etc.: "Wiley's new girlfriend is a real zero (loser)."

1. To direct all of a person's attention to someone or something: "The scientists are trying to zero in on a cure for cancer."

"The math teacher is trying to zero in on why Gina can't comprehend her simple math assignment."

2. To set a measuring device; such as, a scale so it reads 0: "Please zero the scale before you try to weigh the produce (potatoes, onions, etc.)."