re·​ac·​tive | \ rē-ˈak-tiv How to pronounce reactive (audio) \

Definition of reactive

1 : of, relating to, or marked by reaction or reactance
2a : readily responsive to a stimulus
b : occurring as a result of stress or emotional upset reactive depression

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Other Words from reactive

reactively adverb
reactiveness noun

Examples of reactive in a Sentence

The government's response to the problem was reactive rather than proactive.

Recent Examples on the Web

The compounds, called porphyrins, had previously been shown to be adept at absorbing light and using that energy to convert oxygen molecules in the air to a reactive form known as singlet oxygen. Robert F. Service, Science | AAAS, "Crystalline nets harvest water from desert air, turn carbon dioxide into liquid fuel," 3 Sep. 2019 The city is talking with its engineering firm, DOWL, about how to make the water less reactive. Anna Rose Macarthur, Anchorage Daily News, "Bethel water testing shows lead and copper levels exceeding federal standards," 8 Aug. 2019 Emma was diagnosed with reactive attachment disorder, a condition which hampers children's ability to form healthy attachments with their parents, the couple told the news station. Marc Ramirez, Dallas News, "16-year-old Sherman girl missing in Colorado after leaving foster care home," 11 July 2019 The carbon ring is also highly reactive, allowing the researchers to fuse it with other carbon and oxygen rings. Robert F. Service, Science | AAAS, "Carbon atoms marry to form first-ever ring," 15 Aug. 2019 Indeed, the more likely narrative for 2020 is that Trump will stay reactive not become preemptive if tensions with Iran or North Korea lead to violence. Victor Davis Hanson, National Review, "The Economy, Father of Us All," 23 July 2019 There's no need to be reactive in the face of insignificant social mishaps and minor misunderstandings. Tribune Content Agency,, "Horoscope July 15, 2019: Taurus, focus on inner beauty; Leo, dream big and bold," 15 July 2019 Stressed out Some people are naturally more anxious and emotionally reactive, a trait called neuroticism. Carrie Arnold, National Geographic, "If you’re chronically stressed, your dog could be too," 6 June 2019 This shorter time to market means that the company can be reactive, adding extra server capacity near to where it's needed on demand. Peter Bright, Ars Technica, "Satya Nadella: The cloud is going to move underwater," 1 Nov. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'reactive.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of reactive

1717, in the meaning defined at sense 1

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Statistics for reactive

Last Updated

7 Sep 2019

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Time Traveler for reactive

The first known use of reactive was in 1717

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English Language Learners Definition of reactive

: done in response to a problem or situation : reacting to problems when they occur instead of doing something to prevent them
chemistry : tending to change into something else when mixed with another substance


re·​ac·​tive | \ rē-ˈak-tiv How to pronounce reactive (audio) \

Medical Definition of reactive

1a : of, relating to, or marked by reaction reactive symptoms a reactive process
b : capable of reacting chemically highly reactive materials
2a : readily responsive to a stimulus the skin of the geriatric is less reactive than that of younger persons— Louis Tuft
b : occurring as a result of stress or emotional upset especially from factors outside the organism reactive depression

More from Merriam-Webster on reactive

Rhyming Dictionary: Words that rhyme with reactive

Thesaurus: All synonyms and antonyms for reactive

Britannica English: Translation of reactive for Arabic Speakers

Comments on reactive

What made you want to look up reactive? Please tell us where you read or heard it (including the quote, if possible).


readily or continually undergoing change

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