What does "ADD" on rx script mean?

[Adriel]

I was wondering it will just be the strength on the bottom of the lenses

[Ryland]

The ADD means additional power in bifocal lenses. Add powers are commonly between +1.00 to +3.00 .They are used to be adjusted with SPH number for making single vision reading glasses ,computer glasses or bifocal,progressive glasses.Someone may find their ADD value are under the ""N.V."". Unless otherwise specified, both eyes can be assumed to have the same ADD power.

[Lawrence]

Add= Near Addition, means the power strength to be added to the Sphere number for making single vision reading glasses or bifocal and progressive eyeglasses. In this prescription, the Add numbers are put under the Add spaces. Some of the doctors may write one number with sign such as +2.00 in the middle of the space under Add. which means your both eyes have the same Add numbers.