Have it both ways

When we use "no" at the start of a sentence to mean "yes," as you won't be able to stop hearing once you start listening for it, we're employing no as a Janus word

If you need any evidence that English is a beautifully baffling language (in case you're prosecuting it for inscrutability), consider the many words that are also antonyms for themselves

"Cleave" has always struck me as the finest example of this phenomenon, meaning both to cut in two and to adhere together. "Dust" can mean either to clean or to sprinkle with dust. Only context provides the definition.

Once you hear it...

You may not hear it yet, but you soon will. You may already be doing it yourself. I was. And now, I realize, I do it all the time: I use "no" at the start of a sentence to mean "yes." 

It sounded ridiculous when I first heard this NPR story about the phenomenon, which draws from Kathryn Schulz's piece in the the New Yorker: What Part of "No, Totally" Don't You Understand?

It turns out that English once had more options for saying No - no and nea. "No" was a negative response to a positive question, and "nea" was used in response to a question that was phrased in the negative.  The demise of "nea" left us with a problem:

Q: Don't you like the song "Operating" by Hunter Hunted?
A: No. 

Does this mean I hate the song, or love it? 

Schulz theorizes that answering a question in the affirmative by saying "No, definitely" might be a resurrection of the grammatically extinct "nea." But we're extending its usage beyond the traditional. My interpretation is that we're using it to preemptively dismiss all other possible answers. 

Q: Isn't "Summer People" by Kelly Link one of the best stories you've read in a long time?
A: Yeah, no, it's just amazing. 

Witness the real-time transformation of language.