IPA: /ˌriːækˈtɪveɪʃən/
KK: /riːˈæktɪveɪʃən/
The process of making something that was inactive or not working become active again.
The reactivation of the old software improved the system's performance.
Reactivation → It is formed from "re-" (meaning again) and "act" (from Latin "agere", meaning to do or to act) and "-ivation" (a suffix indicating the process of). The word "reactivation" means the process of doing or acting again, particularly in the context of restoring something to a previous state of activity.
Think of 'doing again' ('re-') something that was previously active ('act') — that's why reactivation means bringing something back into action.