In mathematics, an index or power is a small number written to the right and above a base number, which tells how many times the base number should be multiplied by itself. For example, in the expression 2³, 2 is the base and 3 is the index, and it means that 2 should be multiplied by itself three times. The plural of index is indices. Indices are used in algebra to represent repeated multiplication of the same number or variable. The laws of indices are rules for simplifying calculations or expressions involving powers of the same base. Some of the important rules of indices include:

• ya × yb = ya+b
• ya ÷ yb = ya-b
• y-b = 1/yb
• ym/n = (n√y)m
• (yn)m = ynm
• y0 = 1

Indices are used in many areas of mathematics, including algebra, calculus, and geometry. They are also used in physics and engineering to represent quantities such as force, energy, and voltage.