Are Numbers Adjectives? Do They Need a Hyphen?

Here is a common grammar question:

“When do you use hyphens with numbers? For example, is it correct to say 3 feet or 3-feet? And would you write 2 hours or 2-hours?”

Here is the rule to learn: You need a hyphen between two or more adjectives that are used before a noun and act together as a single idea.

This rule also applies to putting a number and a measurement unit together to form an adjective.

For example:

A 50-inch television is too big for this room.

Doctors work 12-hour shifts.

Brian swung the ten-pound sword.

In the sentences above, the measurements, such as 50-inch, describe specific objects, such as television.

When measurements are not being used as adjectives, then hyphens are not needed.

For example:

Haley won the race by 15 yards.

Nine hours later, he was exhausted.

Danielle’s bag weighs eight pounds.

Explanation of how to hyphenate numbers when they are used as adjectives (hyphen is needed) and when they are not (no hyphen)

Let’s test your knowledge with a pop quiz! Choose A or B.

  1. A. I don’t understand why he wrote a 22-page paper on that boring topic.
  2. B.  I don’t understand why he wrote a 22 page paper on that boring topic.
  3. A. I don’t understand why he wrote 22-pages on that boring topic.
  4. B. I don’t understand why he wrote 22 pages on that boring topic.
  5. A. Ashley found a 101-year-old statue at the garage sale.
  6. B. Ashley found a 101 year-old statue at the garage sale.
  7. A. Ashley found a statue that must have been 101-years-old at the garage sale. 
  8. B. Ashley found a statue that must have been 101 years-old at the garage sale. 

Graphic to separate questions from the answer key

Answer Key;

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

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