What‘s the difference between most and mostly？
It was about a newly wealthy black family that moved into a New York City high-rise with mostly white neighbors.

Question

Answer

Most is the superlative (是最的意思): I love chocolate the most.  London restaurants are the most expensive.

Mostly is an adverb and changes the verb (应该是大多的意思）: He eats mostly Japanese food.

Answer

the "ly" part of mostly is just a suffix. example-"Most of his neighbors are white." or "His neighbors are mostly white"