It usually expresses accuracy as a percentage, and is defined by the formula:

Then the Hitchin functional is a functional on 3-forms defined by the formula:

The Jaccard index is defined by the following formula:

The multiplication of two complex numbers is defined by the following formula:

Thus, the tetrations are not clearly defined by the formula given earlier.

The amplitude of the vibration "X" is defined by the following formula.

The phase shift, is defined by the following formula.

The optimal quantization zone width is defined by the following formula:

The number is defined by the formula stating that there exist no elements less than x:

But mass, as related to the 'inertia' of a body, can also be defined by the formula: