The other day on the radio I heard a football coach deride his own game plan: “We played too cautious,” he admitted. My ears recoiled instinctively, knowing the adverb “cautiously” would be the correct way to phrase that sentence.
Most of the time, adding an “ly” to the end of a modifier changes an adjective (which modifies a noun) to an adverb (which can modify a verb, an adjective or another adverb). In some cases, however, that “ly” can cause trouble.
“More important,” the coach added, ” was our inability to execute on offense or defense.”
Or should he have said, “More importantly?”
The correct phrase is “more important,” and the same goes for “most important.” They are often, if not always, shortened versions of “what’s more important” or “what’s most important.”
Using the full phrase “what’s more importantly” in a sentence illustrates the error: “What’s most importantly is that we get good line play,” the coach said. That sentence doesn’t make sense. (Of course, the full version would start, “What’s most important is that…).
Another online source says “more important” and “more importantly” are used interchangeably in all kinds of text and by reputable writers, which means that there’s no reason not to use “importantly.” Except one: It’s wrong. Writers aren’t necessarily grammarians, which is why even writers of high repute can use an editor.
Here’s a cute video from School House Rock about adverbs and what they do.
When you can’t be your own best editor, try another trained set of eyes.