in ‧ ac ‧ tiv ‧ i ‧ ty /ˌɪnækˈtɪvəti, ˌɪnækˈtɪvɪti/ BrE AmE noun [uncountable]
[ Word Family: noun : ↑ act , ↑ action ≠ ↑ inaction , ↑ activity ≠ ↑ inactivity , ↑ reaction , ↑ interaction , ↑ overacting ; adjective : ↑ acting , ↑ active ≠ ↑ inactive ; verb : ↑ act ≠ ↑ overact ; adverb : ↑ actively ]
the state of not doing anything, not moving, or not working:
Don’t suddenly take up violent exercise after years of inactivity.
The time spent between jobs should not be a period of inactivity.