reactor

reactor — noun

1. a large structure or machine that produces heat or electricity by splitting atom

1.nounB2
Definition

a large structure or machine that produces heat or electricity by splitting atoms in a controlled nuclear reaction

Example

The nuclear reactor at the coastal power plant supplies electricity to over two million homes.

countable noun + at + [location]

Engineers shut down the reactor for safety checks after the storm damaged the cooling system.

shut down a reactor for [purpose]

Common collocations
  • nuclear reactor
  • reactor core
  • reactor vessel
  • shut down a reactor
  • reactor design
Synonyms
  • nuclear reactor

    the full form, used for clarity or formal writing

  • atomic pile

    historical term for early reactors; very rare in modern use

Usage Note

Often shortened to reactor in news and everyday conversation. The full phrase nuclear reactor is used when the context is not yet clear.

2. a device, typically a coil or similar component, that limits or controls the flo

2.nounC1
Definition

a device, typically a coil or similar component, that limits or controls the flow of alternating current in an electrical system by opposing changes in the current

Example

The technician installed a reactor to reduce voltage spikes in the factory's power system.

install a reactor to [purpose]

Without a reactor in the circuit, sudden current changes could damage the motor.

Common collocations
  • install a reactor
  • reactor coil
Synonyms
  • inductor

    a broader term for any component that stores energy in a magnetic field; all reactors are inductors

  • choke

    informal term for a reactor designed to block high-frequency alternating current

Usage Note

This sense is technical and appears almost exclusively in electrical engineering contexts. In general conversation, reactor without context nearly always means a nuclear reactor.

Common Mistakes

The electrical reactor changed the voltage.
The electrical reactor helped limit the current in the circuit.
A reactor controls current flow by opposing changes; it does not directly change voltage.

Word family

Synonym discussion

Sense: noun/1

Nuclear reactor is the full technical name and is used in formal writing, safety reports, and engineering contexts — it leaves no ambiguity. Reactor core refers specifically to the central part of a nuclear reactor where the fuel is placed and the nuclear reaction happens, not the whole building or machine. Atomic pile is a historical term for early reactors built from layers (piles) of graphite blocks and uranium fuel; it is rarely used today outside of historical accounts. For example, a news article might say 'the nuclear reactor passed its safety inspection,' while a technician would report on conditions inside the 'reactor core.' The phrase 'atomic pile' only appears in descriptions of the first reactor built in 1942.

nuclear reactorreactor coreatomic pile

Common collocations

Nouns

  • reactor design
  • reactor safety
  • reactor type

Etymology

LatinEnglish

Reactor comes from the verb react, which was formed in English from the prefix re- ('back, again') and the Latin verb agere ('to do, to act'), with the suffix -or added to mean 'a thing that does this action'. The word was first used in the early 1900s for electrical devices that react to changes in alternating current. It was then adopted in the 1940s for nuclear reactors that sustain a controlled chain reaction of splitting atoms, which is now by far the more common meaning.