# Exponentials and indices

When you raise a number to a power, you’re specifying how many times to multiply that number by itself. So for instance, if I have the number ‘5’, and I raise it to the power ‘2’, I’m saying that there should be two ‘5’s multiplying each other:

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There are proper mathematical terms we can use to describe each of the bits in the equation above.

The *base* is the number which is being raised
to a power, the number that has the little index number written above it. It’s
the number that is being multiplied by itself a certain number of times. In
this example, ‘5’ is the base.

The *exponent* or *index number* is the
little number above the base, it tells you what *power* the base is being
raised to. In this example, the exponent is ‘2’.

The *number in decimal notation* is just the number
that the expression evaluates to – for our example, five squared is equal to
twenty-five – ‘25’ is how we write it in decimal notation.