reactive
gb/ɹiˈæktɪv/ us/ɹiˈæktɪv/
B2
English
Senses
0 senses
adjective
B2
property
1
responding after events happen
doing something because something has already happened, instead of planning ahead
Usage pattern:
reactive [approach/strategy/response] to [something]
Common mistake:
Do not confuse reactive with reactionary; reactionary usually means opposed to political or social change.
Synonyms
responsive (more neutral or positive; emphasizes answering needs or changes)
|
defensive (emphasizes protecting oneself after a problem or criticism)
|
after-the-fact (emphasizes that action happens only after something is known)
Antonyms
proactive (acting in advance to prevent or create outcomes)
|
preventive (intended to stop problems before they happen)
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anticipatory (based on expecting something before it occurs)
Collocations
reactive approach
|reactive strategy
|reactive response
|reactive management
|reactive policing
|reactive measures
|reactive policy
|reactive stance
|reactive mode
|reactive mindset
Themes
business
|planning
|behavior
|decision_making
Examples
- The company took a reactive approach, fixing defects only after customers complained.
- Instead of being reactive, the team tried to identify risks before the launch.
- Critics said the new safety rules were reactive rather than preventive.
Learner examples
- We need a proactive plan, not a reactive one.
- His response was reactive because he waited until the problem got worse.
adjective
C1
property
2
easily triggered emotionally or behaviorally
quick to become upset, angry, nervous, or excited because of a trigger
Usage pattern:
[someone/something] is reactive to/around [trigger]
Common mistake:
Reactive does not simply mean active; it means responding strongly to something.
Synonyms
sensitive (broader and often less negative)
|
touchy (informal; easily offended or annoyed)
|
volatile (suggests sudden and intense changes in mood or behavior)
Antonyms
calm (not easily upset or agitated)
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composed (controlled and emotionally steady)
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nonreactive (not responding strongly to triggers)
Collocations
emotionally reactive
|highly reactive
|reactive child
|reactive dog
|reactive behavior
|reactive anger
|reactive parenting
|less reactive
|become reactive
|reactive temperament
Themes
emotions
|psychology
|behavior
|animals
Examples
- When she is under stress, she becomes more reactive to criticism.
- The trainer said the dog was reactive around bicycles and other dogs.
- The therapist helped him notice his reactive anger before he said something hurtful.
Learner examples
- The child is tired and very reactive today.
- Try to stay calm, not reactive.
adjective
technical
B2
property
3
readily undergoing chemical reactions
able to react easily with other chemicals
Usage pattern:
[substance] is reactive with [substance]
Common mistake:
Chemicals usually react with other chemicals; use reactive with when naming the substance they react with.
Synonyms
chemically active (more explicitly about chemistry)
|
unstable (may imply the substance changes or breaks down easily, not just reacts)
|
labile (technical; easily changed or broken down)
Antonyms
inert (does not react easily with other substances)
|
unreactive (direct opposite; not likely to react)
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stable (resistant to change or breakdown)
Collocations
highly reactive
|chemically reactive
|reactive metal
|reactive gas
|reactive chemical
|reactive substance
|reactive element
|reactive compound
|reactive with water
|reactive surface
Themes
chemistry
|science
|materials
|safety
Examples
- Sodium is highly reactive with water.
- The lab stores reactive chemicals in a separate safety cabinet.
- Gold is valued partly because it is much less reactive than many other metals.
Learner examples
- This metal is reactive with water.
- Wear gloves when handling reactive chemicals.
adjective
technical
C1
property
4
showing a medical response
showing that the body or a medical test has responded to something
Usage pattern:
reactive [test/result/lymph node/airway/skin]
Common mistake:
In lab reports, reactive often means positive, but the exact meaning depends on the test.
Synonyms
positive (used mainly for test results when something is detected)
|
inflammatory (emphasizes inflammation as the response)
|
responsive (emphasizes that the body or tissue responds to a stimulus)
Antonyms
nonreactive (showing no detected reaction or response)
|
negative (used for tests when the target reaction or marker is not detected)
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normal (showing no abnormal medical response)
Collocations
reactive test
|reactive result
|reactive lymph node
|reactive airway
|reactive changes
|reactive inflammation
|reactive antibodies
|reactive skin
|nonreactive result
|reactive tissue
Themes
medicine
|health
|diagnosis
|testing
Examples
- The HIV screening test was reactive, so the clinic ordered a confirmatory test.
- The doctor said the enlarged lymph node looked reactive, not cancerous.
- Her skin is very reactive and becomes red after some fragrances.
Learner examples
- The test result was reactive, so she needed another test.
- The doctor said it was a reactive lymph node.
adjective
technical
C1
property
5
responding automatically to events
used about software that updates or responds automatically when data or events change
Usage pattern:
reactive [app/interface/system/framework/component]
Common mistake:
In software, reactive does not just mean fast; it means driven by events or changing data.
Synonyms
event-driven (emphasizes that events trigger the behavior)
|
responsive (emphasizes quick adaptation to input or changes)
|
dynamic (broader; capable of changing rather than remaining fixed)
Antonyms
static (not changing automatically in response to data or events)
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batch-based (processes data in scheduled groups rather than continuously)
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nonreactive (not designed to respond automatically to changes)
Collocations
reactive programming
|reactive system
|reactive application
|reactive framework
|reactive stream
|reactive UI
|reactive data flow
|reactive design
|reactive component
|reactive pipeline
Themes
computing
|software
|programming
|technology
Examples
- A reactive interface updates the chart as soon as new data arrives.
- The developers chose a reactive framework for the live chat feature.
- Reactive systems are common in apps that process continuous streams of events.
Learner examples
- The app is reactive, so the screen updates immediately.
- They built a reactive dashboard.
Grammar
Dictionary form
reactive
IPA
GB/ɹiˈæktɪv/
US/ɹiˈæktɪv/
Syllables & stress
re - act - ive (3 syllables)
Stress on 2nd syllable (act)
Word forms
Adjective
- Base: reactive
Expressions
c-reactive protein
1/sˈi ɹiˈæktɪv pɹˈoʊtˌin/
fixed phrase
technical
blood marker of inflammation
a blood-test marker that can be high when there is inflammation in the body
Examples
- Her C-reactive protein was high, so the doctor checked for an infection.
- The study measured C-reactive protein as a marker of inflammation.
- A normal C-reactive protein result does not always rule out every disease.
reactive abuse
1/ɹiˈæktɪv əbjˈus/
fixed phrase
informal
retaliatory reaction to abuse
when someone being mistreated reacts angrily, and that reaction is then used against them
Examples
- The advocate said the clip showed only the client's reactive abuse, not the months of harassment before it.
- Online discussions of reactive abuse often focus on how provocation can be hidden from outsiders.
- She learned the term reactive abuse after her partner used her one angry outburst to portray her as the problem.
reactive airway disease
1/ɹiˈæktɪv ˈɛɹwˌeɪ dɪzˈiz/
fixed phrase
technical
asthma-like airway symptoms
a medical term for breathing problems similar to asthma, especially when doctors are not sure of the exact cause
Examples
- The pediatrician used the term reactive airway disease until they could tell whether it was asthma.
- Smoke and cold air can worsen symptoms in children with reactive airway disease.
- The emergency note listed reactive airway disease because the patient had wheezing and shortness of breath.
reactive arthritis
1/ɹiˈæktɪv ɑɹθɹˈaɪtɪs/
fixed phrase
technical
arthritis after an infection
painful joint swelling that can happen after some infections
Examples
- He developed reactive arthritis a few weeks after a stomach infection.
- Reactive arthritis can cause swollen joints, eye irritation, and pain when urinating.
- The doctor asked about recent infections before diagnosing reactive arthritis.
reactive attachment disorder
1/ɹiˈæktɪv ətˈæt͡ʃmənt dɪsˈɔɹdɚ/
fixed phrase
technical
attachment disorder from severe neglect
a serious childhood condition in which a child struggles to form close emotional bonds because of severe early neglect
Examples
- The clinician evaluated the child for reactive attachment disorder after a history of severe neglect.
- Reactive attachment disorder is rare and requires careful professional assessment.
- Therapy for reactive attachment disorder often focuses on safe, consistent caregiving relationships.
reactive hypoglycemia
1/ɹiˈæktɪv hˌaɪpoʊɡlaɪsˈimiə/
fixed phrase
technical
post-meal low blood sugar
low blood sugar that happens after eating
Examples
- She felt shaky two hours after lunch and wondered if it was reactive hypoglycemia.
- Reactive hypoglycemia can cause sweating, hunger, weakness, and anxiety-like symptoms.
- The dietitian suggested balanced meals to reduce episodes of reactive hypoglycemia.
reactive oxygen species
1/ɹiˈæktɪv ˈɑksɪd͡ʒən spˈiʃiz/
fixed phrase
technical
oxygen molecules causing oxidation
oxygen-containing molecules that react easily and can damage cells if there are too many
Examples
- Antioxidants help neutralize some reactive oxygen species in the body.
- Excess reactive oxygen species can damage proteins, lipids, and DNA.
- Exercise can temporarily increase the production of reactive oxygen species.
reactive programming
1/ɹiˈæktɪv pɹˈoʊɡɹˌæmɪŋ/
fixed phrase
technical
event-responsive programming style
a way of writing software so it updates automatically when data or events change
Examples
- The team used reactive programming so the dashboard updated whenever new data arrived.
- Reactive programming is useful for apps that handle streams of user actions.
- Learning reactive programming can be challenging because the data flow is often asynchronous.