A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007
Words formed with prefixes
Spelling
Part III. Style 20 spelling
Words formed with prefixes are normally closed, whether they are nouns (postmodernism), verbs (misrepresent), adjectives (antebellum), or adverbs (prematurely). Use a hyphen, however, in these cases:
when the prefix is combined with a capitalized word
sub-Saharan
but
subdivision
pro-Asian
but
pronuclear
when the prefix is combined with a numeral
pre-1950
but
predisposed
mid-80s
but
midlife
to separate two i's, two a's, or other combinations of letters or syllables that might cause misreading
anti-intellectual
but
antidepressant
semi-invalid
but
semiopaque
when the prefix precedes a compound word that is hyphenated or open
non-coffee-drinking
but
nonbelief
post-high school
but
postgame
to separate repeated terms in a double prefix
sub-subentry
when a prefix stands alone
pre- and postwar
macro- and microeconomics
These patterns apply to words formed with the following prefixes, among others.
ante
anti
bi
bio
co
counter
cyber
extra
hyper
infra
inter
intra
macro
mega
meta
micro
mid
mini
multi
neo
non
post
pre
pro
proto
pseudo
re
semi
socio
sub
super
supra
trans
ultra
un
The patterns also apply to prepositions such as over and under that can be attached to words in the same position as prefixes.
overachiever
underhanded
over- and underused