Integers are whole numbers that can be positive, negative, or zero, but have no fractional or decimal part.
The set of integers is denoted by ℤ = {..., -3, -2, -1, 0, 1, 2, 3, ...}. Integers include all natural numbers (1, 2, 3...), their negatives, and zero. Integers are closed under addition, subtraction, and multiplication (result is always an integer), but not under division (result may be a fraction). Integers are used in counting, measuring, temperature, finance, and all areas of mathematics.
Natural numbers were used since prehistoric times. The concept of zero was developed in India around the 5th century CE. Negative numbers were first accepted in Chinese and Indian mathematics but were viewed with suspicion in Europe until the 17th century. The symbol ℤ for integers comes from the German word "Zahlen" (numbers), introduced by mathematician David Hilbert.