“[I]n mod.F. the suffix has become -iser, alike in words from Greek, as baptiser, évangéliser, organiser, and those formed after them from L., as civiliser, cicatriser, humaniser. Hence, some have used the spelling -ise in Eng., as in French, for all these words, and some prefer -ise in words formed in French or Eng. from L. elements, retaining -ize for those of Gr. composition. But the suffix itself, whatever the element to which it is added, is in its origin the Gr. -ιζειν, L. -izāre; and, as the pronunciation is also with z, there is no reason why in English the special French spelling should be followed, in opposition to that which is at once etymological and phonetic. In this Dictionary the termination is uniformly written -ize.
In the last few decades, the suffix -ise has become the more common spelling in the UK. Many people there incorrectly regard -ize as American English, though it has been in use in English since the 16th century. The OED lists the -ise form of words separately, as “a frequent spelling of -IZE…”.” —
I just lost 45 minutes of my life trying to figure out why the British edition book I was reading was able to spell ‘colour’ properly and not ‘characterize’. I still stand by -ISE spellings.