What usually determines when more or most should be used instead of the -er or -est suffix on an adverb or adjective?

Question

Quizplus · Accepted Answer

The number of syllables in the positive form determines when more or most should be used instead of the -er or -est suffix on an adverb or adjective. If the positive form has one syllable, the -er or -est suffix is used. If the positive form has two or more syllables, more or most is used.

What Usually Determines When More or Most Should Be Used