Reactive

Reactive can refer to:

Generally, capable of having a reaction
Reactance (electronics), the imaginary component of AC impedance
In behavioral medicine reactive often refers to a treatment approach where a does not initiate contact as opposed to proactive treatment where the therapist initiates contact with the client e.g. proactive and reactive quitlines for tobacco and alcohol
Reactive mind
The parent company of ReactiveMicro.com

Translation of "Reactive"

French: Réactif.