Near the end of "Eye of the World" in Chapter 52, when Moraine is explaining to the others what cuendillar is, she uses the term ra'angreal:
"Cuendillar, " Moiraine said. "Heartstone. No one has been able to make it since the Age of Legends, and even then it was made only for the greatest purpose. Once made, nothing can break it. Not the One Power itself wielded by the greatest Aes Sedai who ever lived aided by the most powerful ra'angreal ever made. Any power directed against heartstone only makes it stronger."
Later books establish that there are are three types of objects which can enhance one's ability to use the One Power:
- ter'angreal; an object imbued with the Power to serve a specific purpose
- angreal; an object designed to strengthen one's ability to use the Power
- sa'angreal; the most powerful, which can massively increase ability to channel
As far as I could tell, the term ra'angreal is never used again in the series. Either it's a case of the author not yet establishing the terminology (it IS the first book after all), or it's a typo in the physical copy I own (a hardback reprint).
Did Robert Jordan ever comment on this discrepancy, or is it simply a typo that was meant to say sa'angreal?