noun, plural ac·tiv·i·ties.
- the number of atoms of a radioactive substance that disintegrate per unit of time, usually expressed in curies.
Origin of activity
noun plural -ties
- the capacity of a substance to undergo chemical change
- the effective concentration of a substance in a chemical system. The absolute activity of a substance B, λ B, is defined as exp (μ B RT) where μ B is the chemical potential
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.