reactive

adjective

re·​ac·​tive rē-ˈak-tiv 

1

: of, relating to, or marked by reaction or reactance

2

a

: readily responsive to a stimulus

b

: occurring as a result of stress or emotional upset

reactive depression

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

As the Maillard reaction progresses to the advanced stage, thermal breakdown of Strecker aldehydes and aminoketones results in the generation of free radicals and reactive carbonyl (carbon-oxygen-containing) species. — Encyclopedia Britannica, 9 Nov. 2026

Antioxidants Antioxidants are molecules that protect the body by neutralizing free radicals, highly reactive molecules that have been linked to health issues such as autoimmune diseases, diabetes, and cancer. — Lana Barhum, Verywell Health, 8 Nov. 2026

Real programs still produce events nobody could foresee, and that is what reactive capacity is for. — Leslie Ellis, Forbes.com, 6 Nov. 2026

By grafting different polymer chains onto polyolefins, scientists can introduce chemical functionalities that are missing in conventional plastics, including water-attracting groups, acids, bases, or highly specific reactive chemical groups. — Muskan Bhatia, Interesting Engineering, 5 Nov. 2026

Word History

First Known Use

1717, in the meaning defined at sense 1

Phrases Containing reactive

• C-reactive protein
• hyper-reactive
• reactive arthritis

Rhymes for reactive

• active
• tractive
• attractive
• contractive
• extractive
• inactive
• proactive
• refractive
• subtractive
• bioactive
• hyperactive
• interactive

Kids Definition

reactive

adjective

re·​ac·​tive rē-ˈak-tiv 

1

: of or relating to reaction

2

: reacting or tending to react

reactively adverb

reactiveness noun

reactivity

(ˌ)rē-ˌak-ˈtiv-ət-ē 

noun

Medical Definition

reactive

adjective

re·​ac·​tive rē-ˈak-tiv 

1

a

: of, relating to, or marked by reaction

reactive symptoms

a reactive process

b

: capable of reacting chemically

highly reactive materials

2

a

: 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