radiation
Pluralradiations
- 1Energy emitted by radioactive materials as their atoms break down.
Geiger counters click faster as the radiation grows more intense.
Prolonged exposure to radiation can damage living cells.
Similarradioactivity
Note
The meaning that carries fear, and the one most people hear first in news of accidents or bombs. It pairs naturally with level and exposure. "Weird Al" Yankovic's "Christmas at Ground Zero" (1986) jokes about a date going ahead if the radiation level's OK, to see the new mutations. The dark comedy works only because listeners hear radiation as a hazard, not as warmth or light.
- 2Ellipsis of electromagnetic radiation.
Radio antennas detect radiation across a wide range of wavelengths.
Infrared radiation warms your skin even on a cloudy day.
Note
A clipped form: the adjective drops away and radiation alone stands for electromagnetic radiation, as in heat radiation, infrared radiation or radio-frequency radiation. Writers who want the full term without its length use EMR. Because the bare word can also mean radioactive energy, the shortened form relies on context. Infrared warming your skin and whatever makes a Geiger counter click are different things.
- 3The movement of energy through space by means of electromagnetic waves, requiring no material medium.
Unlike conduction, radiation can carry heat across the vacuum of space.
A thermos slows heat loss by reducing both convection and radiation.
- 4The process of emitting waves or particles outward from a source.
The radiation of heat from the engine could be measured with infrared sensors.
Sunspots influence the radiation of charged particles into the solar wind.
Similaremission, release, discharge
Oppositeabsorption
- 5The spreading outward of something from a central point or surface, as rays of light diverge.
The radiation of nerve fibers from the spinal cord forms a complex network.
Map designers illustrated the radiation of trade routes from the ancient capital.
Similardivergence, spread, branching
Oppositeconvergence
Note
The broad image the scientific senses grew from: a borrowing of Latin radiatio, which also reads in English as radiate plus -ion, the noun of the action. Almost anything can spread outward this way, not only light. Nerve fibers, trade routes and even feeling can, as in the radiation of love from a crowd. Used figuratively, it suggests force or warmth felt from a center.
- 6A rapid branching of one ancestral species into many distinct new forms.
The adaptive radiation of cichlid fish produced hundreds of species in a single lake.
Biologists trace the radiation of flowering plants to a burst of new pollinators.
Similardiversification
Note
Evolutionary biology borrows the picture of lines spreading from a point: one ancestral lineage fanning out into many. Here it is firmly a count noun with a plural. Elizabeth Kolbert's The Sixth Extinction (2014) speaks of whole radiations of mammals coming and going. It names its group with of, as in Donald R. Prothero's "the radiation of dogs in South America," and often takes adaptive in front.
Practice
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Origin
Borrowed from Latin "radiatio" (stem "radiationis"). By surface analysis, it can be seen as "radiate" plus the suffix "-ion."