What does runoff mean?
Runoff is water or another liquid that flows away from a surface, usually because it has not been absorbed into the ground. It is common in environmental and agricultural contexts, where phrases such as storm runoff and surface runoff refer to water moving across soil, roads, roofs, or other surfaces and potentially carrying sediment or pollutants with it. Runoff can also mean material that is washed away in this way. In a political sense, a runoff is a second election or contest held when the first vote does not produce a clear winner, usually between the two candidates who receive the most votes. The word is useful because it describes both a familiar environmental process and a distinctive electoral procedure. It is normally a countable noun when referring to a quantity of liquid or material and to an additional election.
Water or another liquid that flows off land or a surface rather than soaking into it.
"The storm generated a large amount of runoff."
Often used in environmental, agricultural, and hydrological contexts.
An additional contest or election held when the first vote does not settle a clear winner.
"The two candidates will meet in a runoff next week."
Common in political and electoral reporting.
The plural is regular and is used for separate quantities of runoff or separate additional contests.
"Flood control measures were designed to reduce runoffs from the surrounding hills."
In politics, a runoff is the extra contest that happens when no candidate wins the first vote outright.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does runoff come from?
Runoff is formed in the 19th century from the verb phrase run off, meaning water that flows away from a surface. Its development follows the ordinary compound-forming pattern of English, in which a noun can be formed from a verb and a particle. The underlying elements are found in related words such as overflow, overrun, and underrun, all of which involve running or flowing beyond a usual limit.
How runoff is actually used
In general use, runoff often describes rainwater that flows over the surface of land rather than entering the soil. In electoral contexts, it denotes a second round of voting, usually between the candidates with the most votes in the first round. The compound is also written as run-off, with a hyphen, in traditional style.
Easily confused with runoff
Runoff and run-off are both used for the same noun, although run-off is the traditional hyphenated form and runoff is increasingly common in modern usage.