activation

https://dx.doi.org/10.1351/goldbook.A00093
This word is used in different senses:
  1. Input of external energy into a chemical system is said to bring about activation of the system.
  2. An added substance that increases the rate of a catalysed reaction is known as an activator, and the effect is called activation. The degree of activation ɛ a is defined by:
    ɛ a = v − v 0 v 0 = v v 0 − 1
    where v 0 is the rate of the catalysed reaction in the absence of the activator and v is the rate of the catalysed reaction in the presence of the activator
  3. When some of the energy required for a reaction to occur is provided by a previous exothermic chemical reaction there is said to be chemical activation.
Source:
PAC, 1996, 68, 149 (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 151