appearance has 4 distinct synonyms spread across 3 of its 6 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 disappearance.
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.
outward or visible aspect of a person or thing
the event of coming into sight
formal attendance (in court or at a hearing) of a party in an action
a mental representation
“I tried to describe his appearance to the police”
the act of appearing in public view
“the rookie made a brief appearance in the first period”
Synonyms, antonyms and the broader and narrower relations for appearance come from Princeton University’s WordNet. Full sources and licences.