The correct spelling of the phrase "most shadow" is /məʊst ˈʃædəʊ/, with the stressed syllable being "shad". The vowel sound in the stressed syllable is pronounced as a short "a" sound as in "cat". The "ow" diphthong in "shadow" is pronounced as in "show", with a rounded lip position at the end. This phrase refers to the area with the greatest darkness caused by an object blocking light, often used in describing the position of the sun or a light source.