A person or thing that is acting or capable of acting. / (electronics) Any component that is not passive. See Passivity (engineering).

Of or pertaining to actuaries. / Relating to statistical calculation, especially pertaining to insurance.

Making active and effective; bringing into a state of activity. / (physics) The process of making a radioisotope by bombarding a stable element with neutrons or protons.

The final real things in the universe, that are "experiential" in nature rather than strictly material. The most basic thing or construct in the universe. Some Whitehead scholars would hold that trillions of Actual Occasions compose one quark. Actual occasions make up everything, even empty space:

(grammar, uncountable) the form in which the subject of a verb carries out some action / (grammar, countable) a form in a particular language used to express the active voice

(astronomy) A galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy.

(dated) Registrar, clerk. [16th-19th c.] / A professional who calculates financial values associated with uncertain events subject to risk, such as insurance premiums or pension contributions.

Of or relating to actinism.

(programming) A value supplied to a method or function, as opposed to a formal parameter.

A part of a book or play in which more things start to happen. The rising action leads to the climax.