When should I use A or An before words starting with a silent s?

When should I use A or An before words starting with a silent s?

You should use "an" before words starting with a silent "s." The use of "an" is determined by the sound of the following word, not the actual letter it starts with. Since the silent "s" does not produce a consonant sound, it is treated as if the word starts with a vowel sound. Therefore, "an" is used before words starting with a silent "s" to maintain proper grammar and pronunciation.