Grammar Numbers as Adjectives |
The Blue Book of Grammar and Punctuation

Numbers as Adjectives

A subscriber recently wrote in with a question that’s a good followup to last week’s Tip of the Week, Writing Numbers:
“When are hyphens used with numbers? Is it 13 feet or 13-feet; 12 hours or 12-hours?”

Rule: Generally, hyphenate between two or more adjectives when they come before a noun and act as a single idea.

This rule can also be applied when a number and a measurement unit taken together form an adjective, that is, when they describe another object.

A 22-inch monitor is too big for my desk.
Nurses work 12-hour shifts.
Anthony swung his five-pound hammer.
In the previous sentences, the measurements, such as 22-inch, describe specific objects, such as monitor.

When measurements are not acting as adjectives, hyphens are not needed.

Suzanne won the race by 25 yards.
Twelve hours later, she was exhausted.
Anthony’s hammer weighs five pounds.

Pop Quiz: Choose A or B.

1. A. I can’t believe she wrote a 33-page treatise on how to screw in a light bulb.
1. B. I can’t believe she wrote a 33 page treatise on how to screw in a light bulb.

2. A. I can’t believe she wrote 33-pages on how to screw in a light bulb.
2. B. I can’t believe she wrote 33 pages on how to screw in a light bulb.

3. A. Harold found a 110-year-old book at the flea market.
3. B. Harold found a 110 year old book at the flea market.

4. A. Harold found a book that must have been 110-years-old at the flea market.
4. B. Harold found a book that must have been 110 years old at the flea market.


1. A.
2. B.
3. A.
4. B.

If the article or the existing discussions do not address a thought or question you have on the subject, please use the "Comment" box at the bottom of this page.

98 responses to “Numbers as Adjectives”

  1. liQuid heaVen says:

    I recently was asked by a friend, “when can you use “I IS”? I said never. He said there is an instance, is this true? And if so, when?

    • Jane says:

      You’re right. You can never use “I is.”

      • Syed. says:

        There is an instance where the usage of “I IS” is possible.
        Example: I is the ninth letter in the alphabet.
        I is a letter followed by J.
        I is the first letter in the word instant.

        One can come up with many such examples.

        • As we replied to Devon on November 23, 2011, that is only correct if the letter I is italicized in the sentence. Individual letters and combinations of letters of the Latin alphabet are usually italicized.

          I is the ninth letter in the alphabet.
          I is a letter followed by J.
          I is the first letter in the word instant.

          • Brenda C Freiheit says:

            How about this sentence: “The fact that she is taller than I is not that important–unless you are buying us clothing!”

            • Your sentence is grammatically correct; however, it may sound awkward to some people due to the omission of the understood word am: “The fact that she is taller than I am is not that important–unless you are buying us clothing!”

  2. Adriana says:

    I have a doubt..when I use the numbers as adjectives, I can say “a one-week trip” for exemple, but why do I use the article a instead an, because one begins in vowel…could you help me? thanks

    • Jane says:

      This is from the site on a vs. an:

      a vs. an

      Rule. Use a when the first letter of the word following has the sound of a consonant. Keep in mind that some vowels sound like consonants when they’re sounded out as individual letters.


      * a finger
      * a hotel
      * a U-turn (pronounced you-turn)
      * a HUD program
      * a NASA study

      Rule. Use an when the first letter of the word following has the sound of a vowel. Remember that some consonants sound like vowels when they’re spoken as individual letters.


      * an FBI case (F is pronounced ef here)
      * an honor (H is silent here)
      * an unusual idea
      * an HMO plan (H is pronounced aitch here)
      * an NAACP convention (N is pronounced en here)

      Deciding whether to use a or an before abbreviations can be tricky. The abbreviation for Frequently Asked Questions (FAQ) causes confusion because it can be pronounced as a word (fak), or one letter at a time (F-A-Q). Using the guidelines above, one would say a FAQ when it is pronounced as one word, and an FAQ when it is pronounced one letter at a time.

  3. D. DeCarlo says:

    What is the proper use of a hyphen in fractions? For example: The Trustee shall distribute one-half of the trust to him.

  4. Karen B. says:

    Could you please indicate the proper way to include the measurement in this sentence? Always have the proper adjustment of 1/8th inch.

  5. wéllen says:

    thank you! your explanations have helped me a lot!

  6. minabey says:

    Could anyone help me out? Which is correct:

    a hundred-thousand-dollar deficit; or
    a $100,000.00-deficit


  7. Miguel F. says:

    Excellent explanation. By the way, and speaking about numbers as adjectives,
    what about these expressions?

    Two-barreled gun, one-legged man, twin-engine (or twin-engined) (either twin-engine and twin-engined appear in may user-created webpages such wikipedia).

    Are they old fashioned? What are they based on and what are they limits?

    Thanks from Spain.

    • Your first two are similar to our examples in the blog “Numbers as Adjectives” and the last, if used with a noun such as twin-engine aircraft, is an example of a compound adjective. These are all grammatically correct. Twin-engine aircraft are still common. We’re not experts on guns, but two-barreled guns were probably more common in the past. “One-legged man” has become a less common expression as medical science has become more adept at fitting people who have lost all or part of a leg with a prosthesis.

  8. Ann D says:

    When using “dozen” to indicate a number of something, is the proper verb usage “is” or “are”? Example: A dozen oyesters (is/are) $4. In this scenario is dozen a noun or an adjective?

  9. maddie says:

    Are numbers and colors considered adjectives? Like, “The Thirteen colonies…” is thirteen a adjective? Or “The blue monkey” ?

  10. Ivan says:

    I am confused. Are numbers adjectives or determiners? How to differentiate them?
    E.g. I’m going to ask you three questions.
    The camel has two humps.
    Which one is adjective? Which one is determiner? Or is it the both of them are of the same word class?

    • Determiners are words placed in front of a noun to introduce and contextualize a noun, often in terms of quantity and possession. Determiners include articles (a, an, the), demonstratives (this, that, these, those), possessives (my, your, our, etc.), and quantifiers (some, few, many, and cardinal numbers). Determiners are always placed in front of a noun. The numbers in your sentences are quantifiers.

      Until recently, traditional grammar and many dictionaries did not take determiners into account. Many determiners were classed as adjectives. Today many grammarians prefer to distinguish determiners as a separate class from adjectives.

  11. HnH says:

    I have a question regarding numbered adjectives. I commonly see nine-tailed with ed but also sometimes nine-tail without ed. Also multi-colored vs. multi-color. Is it safe to assume ed isn’t needed if there’s a measurement associated with the modifier?

    • The phrase nine-tailed is a compound adjective, as in “nine-tailed fox.” We have not seen it written “nine-tail.”

      We are not able to find any authoritative rule regarding the use of -ed with a modifier, although most compound adjectives, like your example above, use -ed. Many writers now use -size instead of -sized, as in a bite-size morsel or a king-size pillow.

      The words multicolored and multicolor do not have hyphens. Most dictionaries, including the American Heritage Dictionary and the Oxford Advanced Learner’s Dictionary, identify both words as adjectives with the exact same meaning and appear to use them interchangeably.

  12. A.J says:

    I know that numbers 1-10 must be spelled out. What about 1.5?

    • Not all authorities agree in the area of spelling out numbers versus using numerals. The AP Stylebook, for instance, recommends spelling out only the numbers one through nine. We recommend writing decimals using figures, but the New Yorker would say “one and a half” or “one point five.” It’s the writer’s call here.

  13. Peter says:

    I have a question. In this sentence, is 15 1/2 an adjective or not? : The bedroom is 15 1/2 ft. long.

  14. Ai says:

    I have troubles with unionist of measurement when they are in front of uncountable nouns.

    There are 3 kilograms of flour in the kitchen or there is 3 kilograms of flour in the kitchen.

    2 meters of fabrics is here or 2 meters of fabric are here.

    Hope I will receive your response soon


    • A quantity of weight or measure is singular when considered as a unit. Also, our Rule 1 of Writing Numbers says, “Spell out all numbers beginning a sentence.” Although an argument can be made for “Two meters of fabric is here” and “There is three kilograms of flour in the kitchen,” to native speakers of English those sentences sound awkward. We suggest rewriting these sentences. For example, “I have two meters of fabric here” and “I have three kilograms of flour in the kitchen.”

  15. Armaun S. says:

    I think there is a problem with the example in rule 8 of the hyphen section.
    This is what it states:

    Rule 8. Hyphenate all spelled-out fractions.

    Example: more than two-thirds of registered voters

    In the example, two-thirds is not acting as an adjective; instead, it is a noun. Therefore, “two-thirds” must not be hyphenated. It should only be hyphenated in cases where it is an adjective, such as: “a two-thirds cup of flour.”

  16. Armaun S. says:

    In Holt Elements of Language, rule 14w states, “Use a hyphen with fractions used as modifiers.” It gives this example:

    two thirds of them [Here, two thirds is not a modifier. Thirds is a noun modified by the adjective two.]

    • Our rules, guidance, and examples are based on areas of general agreement among the authorities. We tend to favor The Chicago Manual of Style and The Associated Press Stylebook. These highly regarded reference books agree on hyphenating fractions in noun, adjective, and adverb forms.

  17. Char W. says:

    Is this correct:
    Three- and Four-Year-Old


    Three and Four Year Old Children………..(a title)

    The former seems complicated and I personally like the later but my proofreader wants the first one. Who is correct or is it just preference?

  18. Islombek Abdullaev says:

    My question is about when to use a noun preceded by a numerical in possessive form and when as a part of a single unit as an adjective: e.g. two days’ leave and a two-day holiday? Thank you in advance.

  19. xlntgson says:

    I’m a 67yr old male tutor or 67-yr old?

  20. Mike G. says:

    Could I simply use the hyphens throughout (i.e., between the numbers and in the compound modifiers) in the following constructions in lieu of suspended hyphenation? Unfortunately, I cannot recast these examples. Oftentimes, the hyphen can be used as the word “to” in this manner.

    a $1-$5-per-month surcharge
    a 3-5-mile hike
    2½-3-hour traffic delays
    15-20%-a-year increase in funding
    2-3-liter bottles of soda
    10-20-gallon containers
    within a 50-100-mile radius
    a 65-75-cent-a-week deduction
    a $10-$15-million-a-year industry
    a $40,000-$50,000-per-year increase in sales
    affects 25-35-year-old men
    affects 25-35-year-olds
    20-25-, 30-35-, and 40-45-year-old men
    20-25-, 30-35-, and 40-45-year-olds

    Good to all above?

    • We recommend inserting “to” in all those constructions. No suspended hyphens, though: a 3-to-5-mile hike, a $10-million-to-$15-million-a-year industry (note added “million” to avoid ambiguity).

  21. Mike G. says:

    So, in other words, anytime “to” is used, place a hyphen on each side of it; but, if we use “and” or “or,” use suspended hyphenation?

    a 20- or 30-year-old male
    10- and 20-gallon containers


    20-to-25-, 30-to-35-, and 40-to-45-year-old men (Is this correct?)

    And are all correct below–yes or no?

    2½-to-3-hour traffic delays
    two-and-a-half-to-three-hour traffic delays
    a 15%-to-20%-a-year increase in funding
    (Repeat % sign twice–yes or no?)
    10-to-20-gallon containers
    ten-to-twenty-gallon containers
    a $40,000-to-$50,000-per-year increase

    And why is it not preferred to use suspended hyphenation in ranges when “to” is used?

    • Regarding your first question, yes to the part about to. There may be rare exceptions, but this is a valuable rule of thumb. With and or or, it depends. Sometimes a suspensive hyphen is needed, but not always. Use it if the sentence is differentiating discrete elements.

      All your other examples are correct. The repeat of the percentage sign in the third example is recommended, as are the two dollar signs in the last example.

      Suspensive hyphenation is not used with to because to usually signals a range, which logic suggests should not be broken up with a space.

      • Mike G. says:

        So these are correct with “or” and “and”?

        a 20-or-30-year-old male
        10-and-20-gallon containers

        And, was this one correct?
        20-to-25-, 30-to-35-, and 40-to-45-year-old

        Thanks again!

        • The following are correct (note the spaces):
          a 20- or 30-year-old male
          10- and 20-gallon containers

          And, was this one correct? Yes, but we wouldn’t recommend such a confusing construction.
          20-to-25-, 30-to-35-, and 40-to-45-year-old

  22. Mike G. says:

    CMOS 16 says:

    If more than one phrasal adjective modifies a single noun, hyphenation becomes especially important{nineteenth-century song-and-dance numbers}{state-inspected assisted-living facility}.

    By adhering to guidance above, are these correct below?

    a two-hour twenty-five-minute eleven-second finish time (no commas and just 3 hyphens?)

    a five-year three-month twenty-day construction project (no commas and just 3 hyphens?)

    Just 2 hyphens in each example below?
    a five-foot ten-inch woman
    an eleven-pound eight-ounce baby

    • Regarding your first two examples, these are the writer’s call. There are no set rules. Different editors have different approaches. We would probably use commas, or rewrite.

      Again, the writer’s call as there are simply no definitive policies we could find. Our thinking is that while you might say “this is a five-foot-ten woman,” you would not say “this is an eleven-pound-eight baby.” Therefore, we’d go with a comma for weight: an eleven-pound, eight-ounce baby but a hyphen for height: a five-foot-ten-inch woman.

  23. LBR says:

    this is super helpful, ty! for writing out large numbers:

    Felling a two-hundred and fifty-foot tree


    Felling a two-hundred-fifty-foot tree

    (something else?)

  24. Tammy says:

    How about
    “2-subcutaneous-injection group”

    Is this OK?
    and is the rule the same as that for
    “2-year-old child”?

    • Sorry, we are not able to help you as we do not understand the meaning of “2-subcutaneous-injection group” as well as we understand the meaning of “2-year-old child.”

  25. Lily says:

    I was wondering if 16 (in 16 years old) an adjective or not?

  26. Linda says:

    Your assistance is appreciated. Which is correct?

    I kindly ask that you allow 3-5 business days for the credits to be built.
    I kindly ask that you allow three to five business days for the credits to be built.

    Thank you.

  27. Mirel says:

    First of all, I want to thank you for your excellent site. It is a wonderful resource.

    Regarding hyphenation before nouns, I’m constantly puzzled by more complex structures, as in sentences such as:
    It contained three hundred and sixty individual digital camera chips.”

    It seems wrong to hyphenate the whole “three hundred and sixty individual digital camera,” or am I wrong?

    How would it be hyphenated, if at all?

    Or: He bought two ¼-scale sized radio-controlled cars?

    Should it be: He bought two 1/4-scale-sized radio-controlled cars?

    Or “two 1/4-scale-sized-radio-controlled cars?

    If possible, I’d love more explanations.

    Thank you!

    • Your first example does not require hyphens. Our post Hyphens with Numbers says, “When numbers are not used as compound adjectives preceding nouns, don’t use a hyphen.” Also, our Rule 8a of Writing Numbers says, “When writing out a number of three or more digits, the word and is not necessary.” However, “digital camera” could be viewed as a compound adjective. Therefore, the sentence should be written It contained three hundred sixty individual digital-camera chips. Your second example contains two compound adjectives. He bought two 1/4-scale-sized radio-controlled cars.

  28. Rohith says:

    Do all the numbers comes under adjectives

  29. Caroline says:

    Is “thirteen-year-old” in the following sentence an adjective?:

    The words fly out of his mouth with a soft-spoken intelligence far beyond that of a thirteen-year-old.

    If not what form of speech is it?

  30. Joel says:

    I am writing a report talking about a setup in a experiment. Which following form I should rather use and if “block” should be plural?
    4-block configuration
    Four block configuration
    Four-block configuration

    Thank you very much for this resourceful website!
    Best regards

  31. Mish says:

    Illnesses have a time of evolution called progress. In med reports, this is usually found with a number of days the person has presented the illness. I dont know if I should say “two-day progress,” “two-days progress,” “two-days’ progress,” or something else. Written differently, I could say “The progress has been going on for two days,” but it’s too long and we appreciate brevity. Can you advise?

  32. Linda Burgess says:

    In the sentence, “there is no difference between the two,” Is “two” still considered an adjective? Or is it now a noun since it is replacing whatever 2 things you’re determining the difference between?

  33. Trina says:

    A co-worker recently asked why we don’t use an “s” to show a plural for the word “hour” in cases such as: 24-hour service, or 8-hour work day?

    • The compound adjectives 24-hour and eight-hour modify the singular nouns service and workday; therefore, the word hour is singular.
      Another way to look at it is that the singular is used to describe and the plural to count.
      We offer 24-hour service.
      We offer service 24 hours a day.

      I have an eight-hour workday.
      I work eight hours each day.

  34. Catarina Pina Gonçalves says:

    Thank you for your explanation. After years seeing English speakers misusing the apostrophe in this way (adjective vs. possessive), I really needed confirmation.
    On a related topic, whenever the noun is used as an adjective, should we not refrain from using plural (as it is with adjectives in English), e.g. “The answer came with a 4 day delay”? Thank you.

  35. Leticia Romero says:

    It’s confusing for me, sorry. I don’t understand the difference between 33-pages and 33 pages.

    • Our post Hyphens with Numbers offers a more thorough explanation. When you are combining two or more words to form a compound adjective in front of a noun, put hyphens between these words (a 33-page book). When numbers are not used as compound adjectives preceding nouns, don’t use a hyphen (the book contains only 33 pages). We suggest you read this post along with the quiz and comments that follow.

  36. Victoria Robbins says:

    My linguistics professor told me that in phrases like “two-floor building” or “eight-page book,” “two-floor” and “eight-page” are nouns simply acting like adjectives, because the final word in the compound is a noun and English is a right-headed language. Now, the logic of this makes sense in a way because the other compound words worked well like this, such as “scarecrow” or “runway,” the second word determining the part of speech. However, I simply can’t wrap my head around the idea that “eight-page” is a noun because no one would ever use it as a noun. Can’t it just be an adjective, an exception to the right-headed rule?

    • As we are not linguists, we will have to respond as grammarians. To us, two or more words that come before the noun they modify and act as a single idea are called compound adjectives, and they are generally hyphenated (see our Rule 1 of Hyphens Between Words). Therefore, for grammarians, two-floor and eight-page in your examples are compound adjectives. These are different from standard compound words such as scarecrow and runway. Your professor probably meant “right-headed” to be more of a guideline than a rule. Consider the word runaway. It is a compound noun meaning “a person who has run away.” It is rare that the word away is used as a noun; it is most frequently an adverb and sometimes an adjective.

  37. KM says:

    If I am referencing more than one century in a sentence, would I use a hyphen? For instance: She is a gallery owner specializing in late 19th and early 20th century decorative arts. And are those two references to the century considered compound adjectives? Thank you!

    • According to the Chicago Manual of Style’s section 7.87: Multiple hyphens, “Multiple hyphens are usually appropriate for such phrases as an over-the-counter drug or a winner-take-all contest. If, however, the compound modifier consists of an adjective that itself modifies a compound, additional hyphens may not be necessary. The expressions late nineteenth-century literature and early twentieth-century growth are clear without a second hyphen.”

      Therefore, we recommend “She is a gallery owner specializing in late nineteenth- and early twentieth-century decorative arts.”
      However, if you were to follow the AP (Associated Press) Stylebook, you would write “She is a gallery owner specializing in late 19th and early 20th century decorative arts.”
      Either method would be acceptable, just be consistent.

  38. Richard says:

    Are the numbers in the following sentences adjectives?

    There were three boys in the pool.
    There were more than 100 people at the party.

  39. M Gatchalian says:

    May I have your 4-digit PIN or May I have your four-digit PIN?

  40. Adam says:

    Can the noun after the number adjectives be plural? Give examples.

    • If you mean 15-foot poles, as in “They installed a row of 15-foot poles” where the “noun after the number adjective” is poles, yes, it can be plural. However, if you mean “They installed a row of 15-feet pole (or poles),” no, that would not be correct.

  41. Abdelnaser says:

    My seventy five ……. old father still works.
    Years _ year’s _ years ‘ _ year

    • The word year is correct in the compound adjective seventy-five-year-old used to describe the noun father in your sentence. As this post states, “Generally, hyphenate between two or more adjectives when they come before a noun and act as a single idea. This rule can also be applied when a number and a measurement unit taken together form an adjective, that is, when they describe another object.” Therefore, write “My seventy-five-year-old father still works.” Please see our rules for Hyphens and Apostrophes for more information.

  42. Tr says:

    Can we say a 50-year loan or a 50-year-old loan?

    • Both terms are grammatically correct; however, the meanings are different. A 50-year loan is a loan with a term of 50 years. A 50-year-old loan is a loan that has been active for 50 years.

  43. Somaia says:

    “The ten neat notebooks of the students …”
    Is ten considered an adjective here?

  44. John says:

    I am 17 years old.
    I am 17.
    In these sentences, are “17 years old” and “17” adjectives or nouns?

    It is 9 o’clock.
    In this sentence, is “9 o’clock” a noun?

    Thank you!

    • says:

      Both the number 17 and the adjective phrase “17 years old” are used as adjectives.

      The phrase “9 o’clock” is an adverb phrase.

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