Grammatically Correct: The writer's essential guide to punctuation ...

GRAMMATICALLY CORRECT
Of little importance or lacking a nonissue, nonevent,
normal positive aspect noninformation
UN-, IN-, IL-, IM-, IR-
Largely the same as non: the
reverse of or absence of
Some words take un
Some take in
Some words starting with I take il
Some words starting with b, m or
p take im
Some words starting with r
take ir
undrinkable, unaltered,
undressed, uninspiring,
unenforced
inattentive, inability, incapable
illegal, illegitimate
imbalance, immobile, implausible
irrefutable, irrevocable
Note, however, that many other words that begin with these
letters take the prefixes in, un or non.
-LESS
Without, devoid of
Unable to do or to be done
-FREE
Unencumbered with; not
containing something
undesirable
witless, shoeless, peerless,
motionless, classless
helpless, countless, resistless
crime-free, smoke-free, frost-free,
caffeine-free
There is clearly a great deal of overlap, which is why you have
to check the dictionary for any word you're not certain of. If no
official negative construction for a word is given, it is usually most
appropriate to create its negative by prefixing it with either un or
non, sometimes adding a hyphen if the combination looks a bit
shaky.
To complicate matters further, in a few cases a negative prefix
differs for different forms of a word: incomplete but uncompleted,
unrepressed but irrepressible, undisputed but indisputable. And
while some base words have more than one acceptable negative
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