The correct spelling of the phrase "most factor" is actually "most of the factor." This can be confusing because "most" is a commonly used word, while "of the" is a more commonly grouped phrase. The pronunciation of "most of the factor" is /moʊst əv ðə ˈfæktər/ with stress on the first syllable of "factor." It's always important to pay attention to small grammar details like these to avoid confusion and spelling mistakes in writing.