A wise writer once said, "If you take hyphens seriously you will surely go mad." Hyphens belong to that category of punctuation marks that will hurt your brain if you think about them too hard, and, like commas, people disagree about their use in certain situations. Nevertheless, if you learn to use hyphens properly, they help you to write efficiently and concretely, and you will have to use them regularly because of the nature of technical writing. Because concepts in science and engineering frequently rely on word blends and complex word relationships, the best writers in these fields master the use of the hyphen.
The Hyphen's Function
Fundamentally, the hyphen is a joiner. It joins:
- two nouns to make one complete word (kilogram-meter);
- an adjective and a noun to make a compound word (accident-prone);
- two words that, when linked, describe a noun (agreed-upon sum, two-dimensional object);
- a prefix with a noun (un-American);
- double numbers (twenty-four);
- numbers and units describing a noun (1000-foot face; a 10-meter difference);
- "self" and "well" words (self-employed, well-known);
- ethnic labels (Irish-American);
- new word blends (cancer-causing, cost-effective);
- prefixes and suffixes to words when the writer wants to avoid doubling a vowel or tripling a consonant (anti-inflammatory; shell-like).
The rule of thumb I apply when using the hyphen is that the resulting word must act as one unit; therefore, the hyphen creates a new word—either a noun or a modifier—having a single meaning. Usually, you can tell whether a hyphen is necessary by applying common sense and mentally excluding one of the words in question, testing how the words would work together without the hyphen. For example, the phrases "high-pressure system," "water-repellent surface," and "fuel-efficient car" would not make sense without hyphens, because you would not refer to a "high system," a "water surface," or a "fuel car." As your ears and eyes become attuned to proper hyphenation practices, you will recognize that both meaning and convention dictate where hyphens fit best.
Self-Study
The following video offers tips on using the hyphen properly:
Transcript: Grammar & Punctuation : When to Use a Hyphen in a Sentence (2:19)
Intro
Hi, I’m here to talk about when to use a hyphen in a sentence. A hyphen sort of looks like a dash, but they’re two different punctuation marks. Uh, a dash is wider than a hyphen. It sometimes is notated as two hyphens put together, and that’s used between words in a sentence to signify a pause, usually. Uh, a hyphen is used to actually connect words.
What is a Hyphen
Such as in this case, the well-known actor. Sometimes it’s used to connect two words that are functioning together as a modifier, so well known is functioning as sort of an adjective to modify actor. Um, now you won’t use a hyphen if you put those words after the word that’s being modified: the actor who was well known.
You also don’t need a hyphen to connect an adverb, such as quickly. A lot of adverbs end in ly, and another modifier in this case, moving, before a noun. If you have a series of modifiers, in this case third, fourth, and fifth grade, those are three different types of students that we’re talking about. Um, and third grade, fourth grade, and fifth grade each individually would be hyphenated. You’ll keep the hyphens in the series and just have that second word at the end of the last one.
There are some other words like cross examine that are hyphenated all the time whether or not they’re modifying anything. Just as nouns, they’re hyphenated. Um, you’ll find those listed that way in the dictionary. Uh, some other words may just be compound words without— they’ll both together without any hyphen in between— and some might be separate words. And if your dictionary doesn’t list them together, then assume that they are separate words.
Hyphens in Numbers
Hyphens also show up in numbers, uh, such as in fractions that are written out like 1/4. Um, and also in compound numbers from 21 to 99, so 33 will have a hyphen between 30 and three.
Finally, you’ll always use a hyphen with the prefixes all, EX, and self, such as ex-wife, and with the suffix elect, so President elect, for example, will have hyphens in all cases.
Examples of Properly Used Hyphens
Some examples of properly used hyphens follow. Note how the hyphenated word acts as a single unit carrying a meaning that the words being joined would not have individually.
Examples
- small-scale study
- two-prong plug
- strength-to-weight ratio
- high-velocity flow
- well-known example
- frost-free lawn
- self-employed worker
- one-third majority
- coarse-grained wood
- decision-making process
- blue-green algae
- air-ice interface
- silver-stained cells
- protein-calorie malnutrition
- membrane-bound vesicles
- phase-contrast microscope
- long-term-payment loan
- cost-effective program
- time-dependent variable
- radiation-sensitive sample
- long-chain fatty acid
When Hyphens Are Not Needed
By convention, hyphens are not used in words ending in -ly... In these examples, no hyphens are needed:
Examples
- finely tuned engine
- blood pressure
- sea level
- real estate
- census taker
- atomic energy
- civil rights law
- public utility plant
- carbon dioxide
Prefixes and Suffixes
Most prefixes do not need to be hyphenated... The following is a list of common prefixes that do not require hyphenation:
Common Prefixes
- after
- anti
- bi
- bio
- co
- cyber
- di
- down
- hetero
- homo
- infra
- inter
- macro
- micro
- mini
- nano
- photo
- poly
- stereo
- thermo
Common suffixes also do not require hyphenation... Typically, you do not need to hyphenate words ending in the following suffixes:
Common Suffixes
- able
- less
- fold
- like
- wise
Commonly Used Word Blends
Also, especially in technical fields, some words commonly used in succession become joined into one... Here are examples:
Common Word Blends
- blackbody
- groundwater
- airship
- downdraft
- longwall
- upload
- setup
- runoff
- blowout