How to Use Hyphens to Create Connections and Clarity in Your Writing
Hyphens might be tiny punctuation marks, but they are powerful tools for adding clarity to your writing. In a basic sense, hyphens are connectors. They bring together words and word components to help readers easily connect and understand concepts.
But how do you know when you should use a hyphen in scientific and medical writing?
In general, hyphens should be used to avoid ambiguity and make the reader’s job easy. But the guidelines for using hyphens are not consistent across styles. Most style guides have many pages of guidelines for how to properly use hyphens—and all the complicated exceptions to those uses. And because language constantly evolves, the guidelines also change over time.
Although different styles have different guidelines, you can start by learning a few key recommendations. Below are some guidelines outlined in the AMA Manual of Style, which is the most widely adopted style in medical and basic science journals.
When to Use Hyphens
Hyphenate compound adjectives that modify a noun
decision-making process (But: process of decision making)
follow-up visit (But: the patient followed up)
T-cell activation (But: activation of T cells)
low-density resolution (But: the resolution was low density)
long-term therapy (But: the therapy was long term)
treatment-related outcome (But: the outcome was related to the treatment)
Some exceptions: peer review process, open access journals, small cell carcinoma (see more examples below)
Hyphenate two nouns that equally contribute to creating a single noun
physician-scientist
doctor-patient relationship
input-output ratio
Hyphenate a compound that starts with a number and precedes the noun it modifies
10-question survey
5-fold increase
half-life
1-mM concentration
Hyphenate coordinating or conflicting adjectives whether or not they precede a noun
The false-positive test results were reported.
The test results were false-positive.
We conducted a double-blind study.
The analysis was double-blinded to the researchers.
Hyphenate words with prefixes when the prefix changes the meaning of the unhyphenated word
re-sent (meaning: to send something again)
resent (meaning: to feel or express annoyance)
re-form (meaning: to form again)
reform (meaning: to change or amend to improve conditions)
re-present: (meaning: to present again)
represent: (meaning: to portray, describe, or serve)
Hyphenate words to avoid awkward letter combinations
anti-inflammatory
de-emphasize
meta-analysis
multi-institutional
Some exceptions: posttranscriptional, preexposure, posttreatment, underrepresented (see more examples below)
Hyphenate words to avoid ambiguity
a small-bowel constriction (meaning: a constriction of the small bowel)
a small bowel constriction (meaning: a small constriction of the bowel)
a single-specialty center (meaning: a center devoted to one specialty)
a single specialty center (meaning: one center devoted to a specialty)
a solid-organ transplant program (meaning: a program for transplanting solid organs)
a solid organ transplant program (meaning: a well-established program for organ transplant)
When Not to Use Hyphens
Some prefixes are not joined by hyphens
ante- (antecede)
anti- (antimicrobial)
auto- (autoimmune)
bi- (bidirectional)
co- (coauthor)
contra- (contraindication)
counter- (countermeasure)
de- (deidentify)
e- (email)
eco- (ecosystem)
extra- (extravasate)
infra- (infrared)
inter- (interoperative)
intra- (intranasal)
micro- (microarray)
mid- (midway)
multi- (multicenter)
non- (nonprofit)
over- (overexpression)
pre- (preoperative)
post- (postoperative)
pro- (proactive)
pseudo- (pseudopregnancy)
re- (repossess)
semi- (semiconductor)
sub- (subliminal)
super- (supernatural)
supra- (suprapure)
trans- (transsacral)
tri- (triglycerides)
ultra- (ultramicrotome)
un- (unconscious)
under- (underrepresented)
Some words that are commonly read together do not need a hyphen
amino acid levels
basal cell carcinoma
birth control methods
bone marrow biopsy
deep vein thrombosis
fresh frozen plasma
health care system
lower extremity amputation
medical school students
multiple organ disease
natural killer cell
open access journal
open heart surgery
peer review process
primary care physician
public health official
small cell carcinoma
soft tissue sarcoma
tertiary care center
Some words lost their hyphens over time
antimicrobial
antioxidant
antiviral
autoimmune
coauthor
codirects
coexist
coexistence
cofactor
coidentity
coinvestigator
countermeasure
coworker
deidentify
downregulation
dysregulation
ecogenetic
interrater
knockdown
midaxillary
midbrow
multicenter
nonexposed
noninfectious
nonnegotiable
nonprofit
nonresident
overexpose
overexpression
overproduction
overrepresented
overtreatment
postinfectionpostinfectious
postnatal
postoperative
posttranscriptional
posttranslational
posttraumatic
posttreatment
preclinical
preexisting
preinfection
reevaluation
reexpress
repossess
transsacral
ultramicrotome
underrepresented
upregulation
Exceptions
These guidelines from the AMA Manual of Style come with many exceptions. And every style—and every agency—has its own set of exceptions. For example, some journals use “upregulation” and others use “up-regulation.” To be sure you use the right style, consult your style guide, author instructions, and/or dictionary.
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