Building Words: Spelling Review Study Guide (page 3)

Updated on Aug 25, 2011


Hyphenated words are words that are connected with a hyphen. Compound words are words that are joined together without a hyphen. Hyphenated and compound words can be difficult to remember, because sometimes even dictionaries disagree on how these words are spelled. Double-digit numbers like twenty-two are always written with a hyphen, and words like basketball and waterfall are always written as compound words. Disagreements arise most often with more modern phrases. A pad that goes under a computer mouse is spelled mouse pad by some people and mousepad by other people. If the word remains in use for a long time, one spelling or the other will probably win out.

There are, however, some rules that can help you remember when to hyphenate. You should use a hyphen

  • when two or more words are combined as a single adjective, such as one-way street, dog-eared page, or two-year-old boy.
  • with words that describe job titles or family relationships, such as editor-in-chief, mother-in-law, or half-brother.
  • after the prefixes ex-, self-, and all- (ex-husband, self-employed, allencompassing),as well as before the suffix -elect (president-elect, governor-elect).
  • when joining a prefix to a capitalized word, such as mid-Atlantic or un-American.
  • with fractions and double-digit numbers that are represented by more than one word, such as one-half, two-thirds, or eighty-three. (Note: this hyphenation rule applies only to the numbers twenty-one through ninety-nine. For example, three hundred and forty-three thousand.)
  • to combine numbers with nouns, as in fifty-dollar ticket, four-year term.
  • to avoid confusion, as when combining two words would create an awkwardly spelled word (shell-like instead of shelllike).
  • to form ethnic designations, such as Chinese-American or Indo-European.


THE PHRASES year-old, years old, and o'clock are common sources of hyphenated confusion. Remember that words used as a single adjective are hyphenated. So in the phrase ten-year-old boy, the words ten-year-old form a single adjective. Notice that there isn't a hyphen between old and boy. This is because boy is the noun that the phrase ten-year-old is modifying. On the other hand, if you said that the boy was ten years old, you would not use any hyphens. In this case, the words ten and years are not being used as one adjective; the word ten is an adjective that modifies years, and the word years is a modifier that describes old.

So far, so good. Here's where it gets tricky. If you want to say your friend is a ten-year-old, the words are hyphenated. "But why?" you ask in shock. "This seems to go against all known laws of nature!" The reason is this: In the phrase ten-year-old, the noun is implied. It is a unique case in which, for some mysterious reason, over the years, the adjective phrase ten-year-old has become accepted as a noun. So to repeat: When the phrase [number]-year-old comes before the noun or is used as a noun, it is hyphenated. If the phrase comes after the noun, it is not hyphenated and is often plural: Ben is five years old.

The final rule involving time is an easy one. Numbers used with the phrase o'clock do not have a hyphen, such as three o'clock or twelve o'clock. The phrase o'clock is a shortened form of "of the clock." It's a strange phrase to have such a prominent place in our daily lives, but at least you know how to spell it now!


In this lesson, we learned that a large percentage of English words come from Latin or Greek. Most words consist of roots, which establish the basic meanings of the words, and prefixes and/or suffixes. When trying to understand words, it can be helpful to divide words into syllables.

Prefixes and suffixes are groups of letters that connect to roots to create words. Prefixes come before the root, and suffixes come after the root. Both suffixes and prefixes enhance or change the meaning of a word. Suffixes also determine which part of speech the word will be. Finally, we learned the rules for hyphenated and compound words.

Practice exercises for this study guide can be found at:

Building Words: Spelling Review Practice Exercises

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