What is the right way to write this an schedule or a schedule ?
a bus schedule
The right way of writing a/an determiners coming from the following; The first thing that you should know is that there is no difference in their meanings. Secondly, we specificliy use "an" in our sentences before word that start with a vowel sound. On the other hand, we use "a" when they start with a consonant sound.
When you look more closely you see that it is really difficult to say "a hour" rather than "an hour" ,or "an ball" rather than saying "a ball" .
Examples are taken from cambridge dictionary.