Noun: strength (for example, in reference to eyeglasses prescription, gravitational force or storms); magnitude.
Voimakkuus also often heard in the plural, voimakkuudet.
You may also see the synonym vahvuus (singular) or vahvuudet (plural) to mean basically the same thing.
In English we use ”prescription” to refer to both what a doctor might write you to take the to pharmacy for medicine as well as for the ”prescription” lenses in our eyeglasses. In Finnish it is two different words, resepti for medicine at the pharmacy and voimakkuus or vahvuus for the prescription strength of your glasses. Resepti also means ”recipe,” or the instructions for preparing food.