Used before countable nouns that talk about one thing.
The sound is important not the spelling.
Used to talk about something not known.
Use A when the H is pronounced as A Hotel
The rules are the same as for using them before normal words.
Put an article before each noun.
An should be used before adjectives that begin with a vowel sound.
Not before an adjective that doesn’t have a noun.
Used to talk about something known.
Do not use The before names.