The New Fowler's Modern English Usage, Revised Edition

act, action | activate, actuate 18
(surface-to-air missile), Unesco (United Nations
Educational, Scientific, and Cultural
Organization), and WASP (White
Anglo-Saxon Protestant). Many words of
this kind, especially those that are the
names of organizations, begin by being
written with uniform capitals and full
stops, and only gradually attain the
status and shape of ordinary words after
constant use: thus U.N.E.S.C.O. -•
UNESCO -> Unesco. Others remain written
with uniform capitals (ASH, SAIT,
SAM, WASP, above) but without full stops.
Still others were written with uniform
lower-case letters virtually from the beginning:
laser (light amplification by
stimulated emission of radiation), radar
(radio detection and ranging), and the US
word snafu (situation normal—all /ouled
up).
2 The limitations of the term being
not widely known to the general public,
acronym is also often applied to abbreviations
that are familiar but are not pronounceable
as words. Thus EC (European
Community), FBI (Federal Bureau of Investigation),
and VCR (vidéocassette recorder).
Such terms are also called
initialisms.
act, action. 1 The distinction between
the two words is not always absolute: we
are judged by our acts or by our actions. In
some of its senses, act (derived in the
14c. from OF arte) refers directly to L
actus 'a doing' and in others to L artum
'a thing done'. In general, action means
'the doing of (something)' and has
tended over the centuries to prevent art
from being used in the more abstract
senses. We can speak only of the action,
not the art, of a machine, when we mean
the way it acts; and action alone has a
kind of collective sense, as in his action
throughout (i.e. his acts or actions as a
whole) was correct, he took decisive action
(freq. involving a series of separate acts).
The actions of a person are usually viewed
as occupying some time in doing, in
other words are the habitual or ordinary
deeds of a person, the sum of which
constitutes his or her conduct. Act, by
contrast, normally means something
brought about at a stroke or something
of short duration. As such it is frequently
followed by o/and a noun (an act of God,
an act of cruelty, folly, madness, mercy, etc.).
2 Action is freely used in the attributive
position (action committee, painting,
photography, replay, etc.). Art cannot be so
used.
3 Both words form part of fixed
phrases, idioms, or proverbs: (act) my act
and deed, Act I (of a play), a variety act (at
a circus, etc.); to put on an act, caught in
the art, clean up one's act, get one's act
together, (action) killed in action, out of
action, to take action, actions speak louder
than words; (colloq.) where the action is (the
centre of activity), a piece (or shane) of the
action (implying participation in some
activity).
action (as verb). In its modern use in
the sense 'to take action on (a request,
etc.)', the word is best left at present
to the tight-lipped language of business
managers, e.g. Dismissal will be actioned
when the balance of probabilities suggests
that an employee has committed a criminal
act-Daily Tel, 1981.
activate, actuate. These two verbs were
on a collision course in general contexts
in the 19c. and activate became obsolete
(and was so labelled in the OED) for a
while. Its substantial use in chemistry
and physics in the 20c. has brought activate
back into prominence. At the present
time, activate is the term used when the
context requires 'to render active' (of
carbon, molecules, etc.), 'to make radioactive'
(Most 0/the elements situated between
boron and calcium have been activated under
the influence ofa-rays—K. W Lawson, 1938),
'to aerate (sewage) as a means of purification',
or some other technical or
scientific sense. It is also widely applied
to much less technical items like burglar
alarms, traffic lights, flight plans, and,
less commonly, to behaviour that is motivated
by some set of circumstances (Are
they activated by concern for public morality!
—Essays & Studies, 1961). Actuate, by contrast,
is much less often encountered in
technical contexts, though in practice
devices, diaphragms, forces, pinions, pistons,
and so on, as shown in 18c. and 19c.
examples in the OED, are still actuated by
this or that instrument or agent. Abstract
qualities like anger, greed, jealousy,
malice, etc. are only grudgingly
activated and more commonly actuated.
There is no guarantee that this state of
affairs is permanent. Examples of actuate: