Use Of The A And An Questions Medium
You should use "an" before words starting with a silent "o." The use of "an" is determined by the sound of the following word, not the actual letter it starts with. If the word following the article "a" or "an" begins with a vowel sound, such as in "an orange" or "an hour," you should use "an." In the case of words starting with a silent "o," like "an honest person" or "an hourglass," the "h" is not pronounced, so the following word begins with a vowel sound, and "an" is used.