The British spelling of the process of removing color or the state of having color removed (the American spelling is decolorization).
From decolorise + -ation (from Latin -atio). British English uses 's' where American English uses 'z' in the suffix, following historical preferences dating back to 18th-century lexicography.
This is a perfect example of why American and British English diverged on 'z' vs 's'—American spelling was influenced by French roots preferring 'z' sounds, while British English maintained older '-ise' endings, but both pronunciations sound identical!
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