Zero (0) is both a number and a numerical digit representing the absence of quantity or a null value.
Zero is the additive identity (a + 0 = a). Any number multiplied by zero equals zero. Division by zero is undefined. Zero is neither positive nor negative and sits at the center of the number line. Zero is crucial as a placeholder in our decimal place-value system.
The concept of zero was a revolutionary mathematical development. The Babylonians used a space as a placeholder (300 BCE). The Maya independently developed zero. The modern concept of zero as both a number and placeholder was developed in India around the 5th century CE by mathematicians like Brahmagupta.