One of the regular features we do on Twitter is “Why we need hyphens”: phrases that have different meanings depending on whether there’s a hyphen. These usually occur when a noun has a compound modifier, that is, a modifier that is made up of more than one word.
The classic example of this is “small-business owner” vs. “small business owner.” Is the owner of a business diminutive, or is the business itself small? Depends on the hyphen.
Some other examples of why we need hyphens:
Because a heavy-equipment operator is not the same as a heavy equipment operator.
Because hazardous-materials training is not the same as hazardous materials training.
Because an invasive-species eradication is not the same as an invasive species eradication.
Because 10-year-old trees are not the same as 10 year-old trees.
Because an anti-child-abuse program is not the same as an anti-child abuse program.
And our favorite:
Because 300-odd editors are not the same as 300 odd editors. (Well, not necessarily.)