Compound Words: When to Hyphenate

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  • Nancy Tuten

    3 July 2015

    Compound Words: When to Hyphenate

    A compound word is a combination of two or more words that function as a single unit of meaning. There are three types of compounds: Those written as single words, with no hyphenation, are called closed compounds—the word “flowerpot,” for example.

    Hyphenated compounds, such as “merry-go-round” and “well-being,” are the second type.

    Those in the third group, called open compounds, are written as separate words—the nouns “school bus” and “decision making,” for example.

    Keep in mind that compounds can function as different parts of speech. In such cases, the type of compound can change, too. “Carry over,” for example, is an open compound as a verb but a closed compound (“carryover”) as a noun and an adjective:

    • The money from that line item will carry over to next year’s budget. [verb form]
    • The money used for the trip was part of the carryover from last year’s budget. [noun form]
    • Carryoverfunds can be used to cover a deficit. [adjective form]

    When you don’t know in which category a particular compound belongs, first try looking it up in a dictionary. You will see there that some compounds are hyphenated regardless of their function in a sentence. For example, “on-site” is a hyphenated compound when it functions as an adjective or as an adverb:

    • The team conducted on-site visits. [adjective form]
    • The team conducted its review on-site. [adverb form]

    The real confusion begins when the compound is not given in the dictionary. That is, it is a compound that is being formed for a very specific situation. In such cases, we have to rely on guidelines provided by the style manual to which we adhere. Our style manual of choice, the Chicago Manual of Style, has a lengthy section devoted to compound words—evidence that the rules are not simple.

    Unfortunately, on this issue even the fairly straightforward rules about hyphens leave some room for a writer’s own judgment. Here is what the Texas Law Review Manual of Style says about using the hyphen to create a compound word: “When two or more words are combined to form a modifier immediately preceding a noun, join the words by hyphens if doing so will significantly aid the reader in recognizing the compound adjective” (20). The “if” clause in that sentence is the tricky part.

    One way to decide if a hyphen is necessary is to see if the phrase might be ambiguous without it. For example, “large-print paper” might be unclear written as “large print paper” because the reader might combine “print” and “paper” as a single idea rather than combining “large” and “print.” Another such example is “English-language learners.” Without the hyphen, a reader might think we are talking about English people who are learning any language (“English language-learners”) rather than people who are learners of the English language.

    On the other hand, no one is going to be confused by the phrase “chocolate chip cookies” or “Saturday morning cartoons.” In other words, the open compounds (i.e., no hyphen) “chocolate chip” and “Saturday morning” are so well known that there is no room for ambiguity. The open compound “high school” is so common, for another example, that we would not hyphenate the phrase “high school students.” We would, however, likely hyphenate “high-risk” in the phrase “high-risk students.”

    The other time we must use hyphenation is to join a word to a past participle to create a single adjective preceding the noun it modifies: “a well-intentioned plan,” for example, or “a horseshoe-shaped bar.” Be aware, however, that we do not hyphenate these same phrases when they FOLLOW the nouns they modify:

    • This is a government-mandated program.
    • The program is government mandated.
    • She is a well-respected student.
    • She is well respected as a teacher.

    Another basic rule is that we never hyphenate compounds that are created with “-ly” adverbs, even when they PRECEDE the nouns they modify: “a fully developed plan,” for example, or “a nationally certified teacher.” Here are more examples:

    • We sent in heavily fortified troops.
    • The troops were heavily fortified.


    • All newly employed nurses must be evaluated regularly.
    • All the nurses on the eighth floor are newly employed.


    • A beautifully designed room can be both relaxing and invigorating.
    • The living room is beautifully designed.


    (See also our other article about hyphenating adjectives preceding nouns.)

    Remember these two important points:

      1. We have three types of compounds: open compounds, closed compounds, and hyphenated compounds.

    Can you spot any errors in the use of compounds in the following sentences?

    1. The situation in the Middle East continues to be a closely-monitored media event.
    2. The Department of Transportation maintains rights-of-way alongside all roadways.
    3. Follow up activities have been scheduled for June and July.
    4. We must follow up on these changes.
    5. Long term planning must be an essential goal of this company.
    6. The committee centers all of its recommendations in performance based standards.


    Answers appear below.

    1. The situation in the Middle East continues to be a closely monitored media event. [No hyphen with an "-ly” adverb, even though here it helps form a compound adjective preceding a noun.]
    2. correct [Webster’shyphenates "right-of-way” and the plural form "rights-of-way” in all circumstances–even when the phrase is functioning as a noun, as in this sentence.]li>
    3. Follow-up activities have been scheduled for June and July.
    4. correct
    5. Long-term planning must be an essential goal of this company.
    6. The committee centers all of its recommendations in performance-based standards.

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