Hyphens with Compound Modifiers: A Tall-Columned Building

What is a compound modifier? What is a modifier? Well, to modify is to change. In the English language adjectives and adverbs are generally the modifiers because they describe (and therefore change) things and actions.  A blue dress can be modified to a red dress with the change of the adjective, or modifier, from blue to red.

She quietly read a book can be modified to She quickly read a book with the change of the adverb from quietly to quickly.

Compound modifiers are two (or more) words put together to form an adjective:

• That is a very well-traveled path.
• The three-year-old boy was throwing his toys.
• That two-foot-high wedding cake looked delicious.
• She is a self-made woman.

Generally, these compound adjectives are hyphenated to show that the two separate words go together in describing something. Usually the phrase is clear without the hyphen, but the hyphen does make reading easier, and sometimes can clear up confusion:

• The tall columned building was hundreds of years old.

Was the building tall? Or were the columns on the building tall?

• The tall-columned building was hundreds of years old.

Now we know we mean the columns were tall.

• The tall, columned building was hundreds of years old.

Now we know the building is tall and has columns. 

Some Exceptions:

Of course there are always exceptions. In fact, some style guides devote pages and pages to this issue. The bottom line is if you cannot figure out whether to hyphenate something or not — and it doesn’t seem to make any difference in meaning — and you cannot find it in the dictionary — or if dictionaries disagree — then take your best guess, but be consistent every time you use the modifier.

1. Common, established compounds do not need to be hyphenated. For example: high school prom (not high-school)
2. Compound proper names used as adjectives are not hyphenated: For example: Supreme Court justice (not Supreme-Court)
3. If the first part of the modifier ends in -ly there is no hyphen:  gently falling snow, slowly moving car

And Finally, One More Important Thing…

When the compound modifier comes after the noun it describes rather than before it, it generally is not hyphenated:

I like well-done steak. I like my steak well done.

She has a three-year-old son. Her son is a three year old or Her son is three years old.

I saw a three-toed sloth. The sloth is three toed or The sloth has three toes.

There are exceptions: Self- is always hyphenated  in a compound whether it comes before or after the noun, as is all (sometimes). 

She is very self-conscious.

He is self-taught.

The self-made success told us her secrets.

I have an all-terrain vehicle.  This vehicle is all-terrain.

I am using all-purpose flour. The flour is all-purpose.

The all-women’s choir will sing. The choir is all women. (In this case I would not use a hyphen).