Thank you Tex2002ans. I'll take a look more at what you mentioned.
As there are something like 6000+ occurrences, regular regex doesn't help too much I thin k, particularly when wanting to verify any changes are indeed wanted, e.g. maybe there should be a hyphen and merely remove the space, or mis-match of terms against a dictionary.
As for PDF, there are works for which there is no eBook or only PDF and they are important enough that it's worth the trouble, as I do not read but study them for years.
With variations in the regex, the calibre method works well:
https://manual.calibre-ebook.com/fun...phenated-words
I then diff compare the changes, as I should be doing anyway. Decent though I haven't checked but I think it uses the calibre dictionary and perhaps not a dict formed from terms in the EPUB so there's a bit more to do but it's ok for now.