A number is a mathematical object used to count, measure, and label. It represents a quantity or value in arithmetic and algebra. Numbers can be classified into different types, such as natural numbers (1, 2, 3…), whole numbers (0, 1, 2…), integers (…-1, 0, 1…), rational numbers (fractions), and irrational numbers (like √2 or π). Real numbers encompass all rational and irrational numbers, while complex numbers extend the concept further by including imaginary units. Numbers are fundamental in calculations, data analysis, and everyday transactions. They form the basis of mathematical operations, from simple addition to advanced equations. Whether used in science, finance, or technology, numbers provide a universal language for quantifying and understanding the world. Their properties and relationships are studied in number theory, a key branch of mathematics.