1. "an" is the article of a noun. it is used as an article for singular nouns that begin with a vowel.
2. if. Although this term is not used as much in the present day, it was used more frequently a number of years ago
1. Drew: Look at the snow tumbling down the mountain.
Scott: IT'S AN AVALANCHE!
2: Drew: I would go to the party an i could drive.