எண் (Number) என்பது எண்ணுதல், அளவிடுதல் மற்றும் சிட்டையிடுதலுக்குப் பயன்படும் ஒரு கணிதப் பொருளாகும். கணிதத்துறையில் பலவகையான எண்கள் உள்ளன. எண்களுக்கான இயல் எண்கள் எண்களுக்கான அடிப்படை எடுத்துக்காட்டாகும். எண்களைக் குறிப்பதற்குப் பயன்படுத்தப்படும் குறியீடானது எண்ணுரு எனப்படும்.

A number is a mathematical object used to count, measure, and label. The most basic examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with number words. More universally, individual numbers can be represented by symbols, called numerals; for example, "5" is a numeral that represents the number five. As only a relatively small number of symbols can be memorized, basic numerals are commonly organized in a numeral system, which is an organized way to represent any number. The most common numeral system is the Hindu–Arabic numeral system, which allows for the representation of any non-negative integer using a combination of ten fundamental numeric symbols, called digits. In addition to their use in counting and measuring, numerals are often used for labels, for ordering, and for codes. In common usage, a numeral is not clearly distinguished from the number that it represents.