I’m reading a dubious post suggesting I should be an optimist.

Apple's definition of optimism

I’m looking up ‘optimism’ in dictionary.app on my mac, and in the Derivatives section it gives op-ti-mist. Each is a link, if you click, you get op, short for operation, ti, the 7th note of a scale, and mist, a cloud of tiny water droplets. Thank you, Apple, that’s truly useful, to be able to determine the meanings of words on the basis of the definitions of their component syllables. How did I ever live without it? Now please explain why there’s no definition for mism.