appreciation has 6 distinct synonyms spread across 3 of its 5 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 depreciation.
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.
understanding of the nature or meaning or quality or magnitude of something
“he has a good grasp of accounting practices”
delicate discrimination (especially of aesthetic values)
“arrogance and lack of taste contributed to his rapid success”
an expression of gratitude
“he expressed his appreciation in a short note”
a favorable judgment
“a small token in admiration of your works”
an increase in price or value
“an appreciation of 30% in the value of real estate”
Synonyms, antonyms and the broader and narrower relations for appreciation come from Princeton University’s WordNet. Full sources and licences.