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Hyphens connect words, prefixes, and suffixes permanently or only in certain configurations. Some compound words always contain hyphens ("free-for-all"). As temporary connectors, hyphens prevent ambiguity, clarify meaning, and indicate word breaks at the end of a line. For complete hyphenation rules, see Chicago Manual of Style. For absolute accuracy, consult the latest edition of Webster's Collegiate Dictionary. The copy editor should follow manuscript and not insert hyphens in terms that are not specifically governed by rules of hyphenation. This may mean a variation from one manuscript to another.
The suffix "-like" is hyphenated if:
After "anti-" when it is combined with a substance or a species and modifies words such as antibody, antiserum, or any of the immunoglobulins (IgG, M, A, D, and E).
anti-peptide antiserum
anti-yeast CS1
anti-rabbit IgG
anti-Ras activity
anti-cdc252 antibody
anti-tubulin
exceptions
antibody
antiserum
antioxidant
Before the suffix "-fold":
for numbers less than 10, the suffix is bumped; i.e., there is no hyphen
twofold
ninefold
in a combination of single-digit numbers, only the first has a hyphen
two- and fourfold increases
in a combination of single- and double-digit numbers in the same sentence, use numerals
8- and 10-fold increases; 3- and 3.5-fold increases
follow the same rules for ranges
a seven- to ninefold increase; an 8- to 12-fold increase
After "quasi-," but only when used as an adjectival compound.
quasi-public (adjective)
quasiparticle (noun)
After all prefixes preceding a proper noun, a number, or an abbreviation.
trans-Golgi network
mid-1960s
non-GABAergic responses
When the prefix ends in "a" or "i" and the word begins in "a" or "i," respectively:
intra-arterial, anti-immune.
With suffixes -type, -elect, and -designate.
Valsalva-type
chair-elect
secretary-designate
Between two words that together function as an adjective (and precede the noun). Note: not all compound adjectives are hyphenated. Always consider meaning. If the phrase is ambiguous (e.g., "plasma membrane enriched fraction" — is the membrane enriched or is the fraction?), query the author. Follow the author's lead, and use the following guidelines:
when both words are adjectives used coordinately, regardless of whether they precede the noun
We performed a double-blind test; the test we used
was double-blind.
The test results were false-positive; the false-positive results were
recorded.
when an adjective and a noun are used together as a modifier
high-amplitude wavelength
large-field pattern
long-term effects
low-voltage current
steady-state expression
well-known study
when the second word is an adjective
voltage-dependent properties
cell-specific voltage
trajectories
APV-resistant cell
ATP-free electrodes
when a noun and a present or past participle function together as an adjective
burst-generating mechanisms
Teflon-insulated wires
calcium-sensing receptor
cAMP-mediated epithelial chloride secretion
IGF-binding protein
kinase-signaling pathway
calcium-transporting epithelia
hyperpolarization-activated current
fluorocarbon-simulated ischemia
For three or more words used as an adjective, or two words used as an adjective when the first word has a normally unhyphenated prefix.
analog-to-digital converter
length-to-width ratio
non-insulin-dependent diabetes
out-of-phase inhibition
signal-to-noise ratio
note exception
very low-density lipoprotein
Between a number/word combination used as an adjective:
two-dimensional
single- and double-stranded
8- and 12-cell stage (see $$$Numbers, Numerals, and Math
Signs)
Between the numerator and denominator of a spelled-out fraction, unless either is already hyphenated:
one-third
five thirty-seconds
To spell out compound numbers from 21 to 99.
twenty-one
forty-four
ninety-nine
To express two parts of a whole.
95% O2-5% CO2
With a number and a single unit of measure when used as a modifier, or when a number and unit of measure is part of a compound adjective.
a 12-kDa fragment
a 25-km run
3 × 4-cm strip
2-μm-diameter tip
a 3-cm-diameter tube
1-mm-thick disk
2-μm-thick sections
To separate locants (numbers, element symbols, small caps, Greek and italic letters) and configuration descriptors from the syllabic part of a chemical name:
D-arabinose
N-methylmethanamine
3-chloro-4-methylbenzoic acid
trans-2-bromocyclopentanol
F-actin
To separate a Greek letter preceding or following a term:
α-adrenergic receptor
γ-aminobutyric acid
When combining letters and numbers in a model or catalog number:
SQ-19844
Between amino acids in a known sequence (see CBE, 5th ed., p. 216, and Amino Acids).
Gly-Lys-Ala-Arg-Asp
Other commonly encountered scientific terms that require a hyphen include:
afferents
Ia-afferent
Ia-afferent terminal
amino acid terminals (when used as an adjective; see below)
COOH-terminal
NH2-terminal
Ia-terminal
axes
y-axis
x-axis
intercepts
y-intercept
receptor agonists/antagonists
acetylcholine M1-receptor antagonist
AT2-receptor antagonist
statistical tests
Student's t-test
F-test
sutures
6-0 silk suture
The following prefixes are not usually hyphenated:
anti, bi, co (coworker), contra, counter, de, extra, infra, inter, intra, micro, mid, multi, non, over, peri, post, pre, pro, proto, pseudo, re, semi, sub, super, supra, trans, tri, ultra, un, under
Exceptions include "co-occurence" and "un-ionized". Also, some prefixes with a technical meaning may be hyphenated (see "anti-", above). As always, defer to Webster's Collegiate Dictionary (latest edition).
For a two-word modifier when the first word is an adverb ending in "-ly":
slowly depolarizing voltage ramp
poorly clamped neurite membrane
densely packed tissue
highly refractile cells
genetically manipulated mice.
if the adverb does not end in "-ly", use a hyphen
well-known fact
fast-acting drug
unless it is superlative
best known example
least significant difference
When a normally hyphenated compound adjective follows a linking verb and does not precede a noun; i.e., when it functions as a predicate adjective:
hyphenate
Light-adapted retinal slices...
do not hyphenate
The retinal slices were light adapted...
To spell out a number above 99:
one hundred ten (not one-hundred)
For combination forms of anatomic or directional adjectives:
vestibuloocular
spinocervical
spatiotemporal.
For Latin or foreign phrases used as adjectives:
post hoc testing
an a priori argument
an in vitro experiment
For compound nouns that are well established in the field:
amino acid receptors
fast Fourier transform
pentobarbital sodium anesthesia
soft tissue mass
inner ear disorder
angiotensin converting enzyme inhibitor
whole kidney measurements
Compound nouns composed of two nouns do not require a hyphen, nor do adjectives that modify them. If the compound noun is itself used as an adjective, it does not require a hyphen (though if the author hyphenates it consistently, do not change).
tail temperature
subcutaneous tail temperature
tail temperature measurements
however, author may use
tail-temperature measurements
When two separate adjectives modify a single noun:
euglycemic hyperinsulinemic clamp
primed continuous infusion
paracrine signaling machine
Do not hyphenate a number and unit modifier if the unit of measure has two or more parts.
a 4 ml·kg-1·h-1 rate of infusion
Do not use a hyphen when the numeral and unit are followed by a compound. Authors may also use the word "of"; do not change if this is done consistently.
165 mM
MgCl2
165 mM of
MgCl2
Other commonly encountered scientific terms that require a hyphen include:
bars
bar 2
bands
M band, Z band
I band
cells and cell lines
X cell, N cell, NK cells
connectors
Y connector
fibers
group II fibers
A fiber
however, Iα-fiber (Greek letter)
laminas
A lamina
neurons
C neuron
F neuron
pathways
Ia pathway
piece
T piece
potentials
S potential
receptors
X receptor
D2 receptor
A receptor
however, α1-receptor (Greek letter)
reflexes
H reflex
spikes
SS spike
terminus (when used as a noun; see above)
COOH terminus
NH2 terminus
tubules
t tubule
waves
H wave
zones
a zone
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last edited 10/08/03