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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.

Posted on Thursday, March 5, 2009, at 4:07 pm


32 Responses to “Numbers as Adjectives”

  1. liQuid heaVen says:

    Hi. 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.

        • Jane says:

          As I 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.

  2. zuriel says:

    My daughter’s school has this practice of asking the pupils to clap their hands once and then keep quiet. Some teachers do it by saying “Give me a silent clap.” while others say “Give me a silence clap.” Should it be a ‘silence clap’ or a ‘silent clap’? How do I explain to my daughter?

    • Jane says:

      Actually, neither expression makes much sense and would be called an oxymoron. But if you have to choose, then “silent clap” because “silent” is an adjective describing “clap” while “silence” is a noun.

      • Alexander says:

        (Five years later someone finds through link in the comments on a lesson in French; oh, Internet…)

        Actually, I believe that in this case it’s more correct to say silence clap, as the clap marks the beginning of a few moments of silence. Like “safety goggles” are for safety.

        A silent clap would be a clap that’s inaudible and that’s not what they’re doing in the classrooms (even though they just do the one and single clap)

  3. Adriana says:

    Hi, 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.

  4. 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.

  5. 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.

  6. wéllen says:

    thank you! your explanations have helped me a lot!

  7. minabey says:

    Hi! Could anyone help me out? Which is correct:

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


  8. devon says:

    There are several instances where you can say “I is”, and I am not talking about Ebonics:) Are you ready? Here we go; I is a proper noun. I is the ninth letter in the alphabet. I is a vowel. I is the first letter in the word impressive. Mkay?;)

    • Jane says:

      You are correct; however, Chicago Manual of Style’s Rule (7.58) states, “When a word or term is not used functionally but is referred to as the word or term itself, it is either italicized or enclosed in quotation marks.”
      For instance:
      I is a proper noun. OR “I” is a proper noun.

  9. 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.

    • Jane says:

      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. I’m not an expert 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.

  10. 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?

    • Jane says:

      Dozen is a collective noun. It is singular in this context. The whole set costs $4, not each individual oyster. A dozen oysters is $4.

  11. maddie says:

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

  12. Ivan says:

    Hi! 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?

    • Jane says:

      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.

  13. HnH says:

    Hi, 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.

  14. 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.

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