activation

This word is used in different senses:

Input of external energy into a chemical system is said to bring about activation of the system.
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
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.

Also contains definition of: degree of activation