9 Grammatical Pitfalls
c.1400, "active or secular life," from Old French activité, from Medieval Latin activitatem (nominative activitas), a word in Scholastic philosophy, from Latin activus (see active). Meaning "state of being active, briskness, liveliness" recorded from 1520s; that of "capacity for acting on matter" is from 1540s.
activity ac·tiv·i·ty (āk-tĭv'ĭ-tē)
A physiological process.
The presence of neurogenic electrical energy in electroencephalography..
An ideal concentration for which the law of mass action will apply perfectly.
The intensity of a radioactive source.
The ability to take part in a chemical reaction.