Some words that start with S are sacrilegious, sacrosanct, sardonic and satirical. Learning these words could be useful preparation for the SAT, according to Vocabulary.com.
Some more words beginning with S that might be useful for the SAT are salubrious, which means "promoting health," and slack, which means "not tense or taut." A list of 100 such words is available on Vocabulary.com
Knowing many words that start with S can be helpful for solving crossword puzzles or playing scrabble. WordFind.com has lists of words starting with S, which are arranged by the number of letters in the word. There are three two-letter words starting with S that can be used in Scrabble, which are sh, si and so. There are also 64 three-letter words starting with S, including sir, spy and sum. Players can use all their Scrabble letters by playing a seven-letter word that starts with S, such as salvage.
Another source of words that start with S is Crosswordsolver.org. The list of words starting with S provided by this site includes some proper nouns, such as "Saale River," as well as acronyms, such as "S.U.V." These words are not valid in Scrabble, but they can be very useful for solving crossword clues.