the relative speed of progress or change | changing location rapidly |
amount of a charge or payment relative to some basis | a central nervous system stimulant that increases energy and decreases appetite; used to treat narcolepsy and some forms of depression |
a quantity or amount or measure considered as a proportion of another quantity or amount or measure | a rate (usually rapid) at which something happens |
a magnitude or frequency relative to a time unit | the ratio of the focal length to the diameter of a (camera) lens system |
| distance travelled per unit time |