reactive
UK: riˈæktɪv | US: riˈæktɪv
adj. showing a response to a stimulus
adj. (chemistry) tending to participate in chemical reactions
adj. (behavior) acting in response to a situation rather than initiating change
The word "reactive" originates from the Latin prefix re- (meaning "back" or "again"), combined with act (from Latin agere, "to do"), and the suffix -ive (forming adjectives). The term evolved through Old French (reactif) into English, retaining its core meaning of "responding to an action." In chemistry, it gained specificity to describe substances prone to chemical responses. The modern sense of behavioral reactivity (responding rather than initiating) emerged in the 19th century.
The material is highly reactive to water, producing bubbles immediately.
Her reactive approach to management often led to missed opportunities.
Sodium is a reactive metal that must be stored in oil.
The child’s reactive behavior worsened under stress.
The sensor becomes reactive when exposed to light.