Is there epub-specific html markup you could add to changed words to indicate their original spelling? Like alt text for images, but in a span around a word?

Is there epub-specific html markup you could add to changed words to indicate their original spelling? Like alt text for images, but in a span around a word? There's the html "title" attribute, of course, which would work (mouseover shows the title attribute's value), but that isn't semantically correct for the purpose.