Compound words: open, closed, hyphenated

This edition of Writing Rules is a refresher on compound word usage!

Compound words can be written in three ways:

• Open compounds (spelled as two words, e.g., ice cream)
• Closed compounds (joined to form a single word, e.g., doorknob)
• Hyphenated compounds (two words joined by a hyphen, e.g., long-term).

A common spelling quandary writers face is whether to write compounds as separate words, one word, or hyphenated words.

Open compound words

An open compound word is created in cases when the modifying adjective is used with its noun to create a new noun. When adverbs ending in -ly combine with another word, the resulting compound is always spelled as two separate words.

Example: The next full moon will occur Friday, June 5, 2020.

Example: I blame my recent telescope purchase on my newly discovered passion for astronomy.

Closed compound words

Closed compound words look like one word. At one point, these words weren’t used together, but they’re now accepted as a “real word” in the English language. Interestingly, as the language evolves, we’re seeing more words that begin as hyphenated compounds turning into closed compound words.

Example: I have a notebook full of messy doodles of stars and planets.

Example: I purchased “The Fabric of the Cosmos,” by physicist Brian Greene, from my local bookstore.

Hyphenated compound words

In most cases, a compound adjective is hyphenated if placed before the noun it modifies, but not if placed after the noun.

Example: While dark sky sites can inspire new stargazers, a better long-term solution for driving new interest is connecting people with the night sky in their cities.

But, there is no hyphen here: Dark sky sites are inspiring for new stargazers, but not a good solution for the long term.

When writing this post, we referenced this blog post by our client, Grammarly.