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

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

You should use "an" before words starting with a silent "t." The choice between "a" and "an" is determined by the sound that follows the article, not the actual letter. When the following word begins with a vowel sound, such as "an hour" or "an honest person," you use "an." Since the "h" in "hour" and the "h" in "honest" are silent, the words are pronounced with a vowel sound, and therefore, "an" is used.