preparation has 12 distinct synonyms spread across 7 of its 8 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is resolution.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the activity of putting or setting in order in advance of some act or purpose
“preparations for the ceremony had begun”
a substance prepared according to a formula
“the physician prescribed a commercial preparation of the medicine”
the cognitive process of thinking about what you will do in the event of something happening
“his planning for retirement was hindered by several uncertainties”
the state of having been made ready or prepared for use or action (especially military action)
“putting them in readiness”
(music) a note that produces a dissonant chord is first heard in a consonant chord
“the resolution of one dissonance is often the preparation for another dissonance”
activity leading to skilled behavior
preparatory school work done outside school (especially at home)
the act of preparing something (as food) by the application of heat
“cooking can be a great art”
Synonyms, antonyms and the broader and narrower relations for preparation come from Princeton University’s WordNet. Full sources and licences.