Hyphens are among the most challenging punctuation marks. In two phrases that seem very much alike, one will have a hyphen and one will not.
Consider an example. Would you add hyphens to the following sentence?
Syntax Training is celebrating its 30th anniversary in Seattle with a 30 percent discount on all online courses.
Would you insert a hyphen in 30th anniversary? Would you add one to 30 percent? Think about your answer before scrolling down to read mine.
There's no reason for any hyphens in that sentence. It is correct as is.
Before I explain the rules, let me tell you that the sentence is true! I moved to Seattle from Boston in September 1989 and started Syntax Training shortly thereafter. To celebrate my 30th anniversary of moving to Seattle, I am offering a 30 percent discount (no hyphen!) on all four Syntax Training courses throughout September 2019.
Just use the coupon code 30thanniversary in the shopping cart at Syntax Training's online course site through September 30.
Explanation of 30th anniversary:
No hyphen is needed in the sentence "Syntax Training is celebrating its 30th anniversary in Seattle" because 30th is a simple adjective describing the word anniversary. There is no compound phrase that needs to be held together with a hyphen.
In contrast, these sentences do each need the hyphen shown:
- The 30th-anniversary celebration takes place on October 1.
- The company paid for the couple's 30th-anniversary cruise.
- The 30th-anniversary discount is substantial.
The reason for the hyphens above is that "30th-anniversary" is used as a combined unit to describe the celebration and the cruise and the discount. There weren't 30 celebrations or 30 cruises or 30 discounts; there were one 30th-anniversary celebration, one 30th-anniversary cruise, and one 30th-anniversary discount.
Explanation of 30 percent discount:
The explanation is simple: a number with the word percent is not hyphenated--not even when the percentage describes a thing (like a discount).
These sentences are correct:
- Syntax Training is offering a 30 percent discount on online courses during September.
- The 20 percent increase in costs worried the business owner.
- The 3 percent drop in the homelessness rate was a small step in the right direction.
The Chicago Manual of Style documents this choice with the example "a 10 percent increase." It states that noun and adjective forms of a number and the word percent are always open--meaning unhyphenated. It stipulates that an en-dash is required in number ranges such as "a 30–40 percent increase." Notice that even in the number range example there is no hyphen before the word percent.
The Associated Press Stylebook 2019 gives the example "a 30% increase." AP uses the percent sign (with no spaces) rather than spelling out the word percent in most cases. For casual uses such as "a zero percent chance," it recommends words rather than figures.
Do you have questions about hyphenation or punctuation in general? Take my course Punctuation for Professionals. Be sure to register this month (September 2019) and use the coupon code 30thanniversary for a 30 percent discount (no hyphen!).
Finally, are the hyphens in the title of this post correct or wrong?
As is, the hyphenation is completely wrong. However, if it said "30 Percent Discount for 30th-Anniversary Celebration" the anniversary hyphen would be correct.
Do you agree?