Compound Words - Not as straightforward as we may think

Have you ever been drafting a presentation, a press release or email and wonder if the compound word you're using is one word or two?  After writing for a while even the most simple words tend to look incorrect and spell check does not always clear up this question. I’m talking about such words as checkup, timeframe, or placeholder.

As it turns out, the rules for compound words aren’t straightforward. (Or is that straight forward?)

“Compound words generally develop over time through use. As people continue to use two or more previously unrelated words together, the combination gains acceptance. Unfortunately, this progression doesn't follow a consistent, regular pattern. Word experts can't even agree on rules for compound words,” says the website

A common pattern is that two words — fire fly, say — will be joined by a hyphen for a time — fire-fly — and then be joined into one word — firefly.

This answers the question of why style guides differ on whether compound words such as health care and website are one word or two. The only way to be certain is to look it up in the dictionary (though dictionaries differ on some terms), but here are some guidelines, should you ask yourself at some point is this one word or two?

There are three forms of compound words:

the closed form, in which the words are melded together, such as firefly, secondhand, softball, childlike, crosstown, redhead, keyboard, makeup, notebook;

the hyphenated form, such as daughter-in-law, master-at-arms, over-the-counter, six-pack, six-year-old, mass-produced;

and the open form, such as post office, real estate, middle class, full moon, half sister, attorney general.


Compound nouns are usually written as one word.

Our last editor had a breakdown over serial commas.
What is the payoff for having a house style guide?

Compound verbs are generally written as two.

Please break down your last paragraph into shorter sentences.
I hope to pay off my student loans by June.

Compound adjectives and adverbs are very often written as two words or with a hyphen.

The cake landed upside down. (adverb)
The upside-down painting confused us all. (adjective)

The exception to this rule: Never hyphenate phrases that are created with adverbs ending in –ly.

Our offices were bigger in the recently-renovated building.
April had the dazed look of a newly hired media relations professional.

This does bring the question of when and how to use a hyphen’s.  That will be another blog post.