Does anyone know how to entirely replace, or add, an entire OS X spelling dictionary? I've got a bit annoyed with the 'British English' dictionary because (understandably) it requires spellings in -ise, -isation, -iser, etc. However, the preferred Oxford English Dictionary spellings, which I prefer to use consistently in my writing, are in -ize, -ization, -izer, -ized. There are also some other precise points, e.g. judgment (Oxford spelling) vs. judgement (Cambridge spelling). I've got a bit annoyed with having to add words which are spelt as I want them to my custom word list. Also, it's helpful to have a proper dictionary to flag up the time when I drop the ball and want to write 'advertize' (which is absolutely wrong, since it's not a Greek word in origin). The IANA has created a separate designation for Oxford spellings called en-gb-oed (the 'ordinary' British spellings are en-gb). Someone has produced a complete en-gb-oed wordlist designed for use in Mozilla products (Firefox, Thunderbird, etc.), which you can find here. The list, when unzipped just contains every word on a separate line. So, my question is, is there an easy way to convert this into an OS X-compatible spelling dictionary, either by replacing the contents of British English (en-gb), or by producing a new language option, Oxford English (en-gb-oed)? I know this is a bit niche, but I don't think I can be the first person to want to do this sort of thing.