What made Oprah Winfrey's speech at the Golden Globes so incredibly powerful? Yes, of course, Oprah is a seasoned communicator. She was armed with searing material and propelled by the full weight of justice at her back. And sure her speech was well written and peppered with classic, effective rhetorical devices.

When University of Washington speech coach Matt McGarrity listened to Oprah, he heard all those things. In fact, in a recent, useful Quartz piece he lays out her technical tricks for everyone to benefit from. But the real reason the speech instantly ricocheted around the world and drove speculation of a presidential run wasn't any of these features.

No, insists McGarrity, the most important factor behind the speech's incredible reception wasn't any particular word choice or trick of delivery, instead is was kairos.

What ancient Greek can teach us about Oprah's speech

What's kairos? For those of us over here in the Greek world that's not hard to answer. Kairos is the Greek word for occasion, when something occurs. But according to McGarrity the word had a deeper meaning when it came to the ancient Greeks' study of the art of rhetoric.

"In ancient Greek, kairos was a sense of time. Chronos was the ticking of the clock; kairos was the 'opportune moment.' That chance to say just the right thing, in just the right way, at just the right time. Classical rhetors chased kairos; trained for it," he explains.

Making a great speech, on other words, isn't just about what you say, it's about when you say it. The best talk in the world will land flat if it's introduced at a moment when the audience isn't ready to hear it (just as, entrepreneur readers will note, even excellent, groundbreaking products fall flat if they're out of the sync with the market). Following on a tsunami of allegations of sexual impropriety and abuses of power, Oprah's speech could not have been better timed.

In business as in Hollywood 

This is a reality that modern politicians use to their advantage all the time. "We still privilege kairos. Modern presidential debate seems focused on finding and exploiting the 'just right response,'" insists McGarrity. But it also seems like a lesson in effective speaking that business people would do well to remember too.

You can marshal every statistic in the world for your case and work on your delivery until it's TED-worthy, and still fail to make an impact if your audience isn't prepared to listen to what you have to say.

Ensuring a positive reception might mean delivering your tough talk on the need for cutbacks at a time when the company's financial vulnerability has been recently made glaringly apparent. It might mean seeding the ground with private conversations before your big speech to warm up key players to your message. It might mean piggybacking on industry news, or using the recent troubles of a competitor as an cautionary example.

Whatever form your concern with kairos takes, the message is clear -- timing matters. 

"Yes, Winfrey's speech was well written, but more importantly, it was well timed," concludes McGarrity. If you want your next big speech to have an equally forceful impact in your own corner of the world, you need to be just as thoughtful about when you choose to deliver it.