changing location rapidly | a canal for a current of water |
a central nervous system stimulant that increases energy and decreases appetite; used to treat narcolepsy and some forms of depression | a contest of speed |
a rate (usually rapid) at which something happens | any competition |
the ratio of the focal length to the diameter of a (camera) lens system | people who are believed to belong to the same genetic stock |
distance travelled per unit time | (biology) a taxonomic group that is a division of a species; usually arises as a consequence of geographical isolation within a species |
| the flow of air that is driven backwards by an aircraft propeller |