So many students don’t seem to have a concrete plan for when to use the article a and when to use the article an. They are NOT interchangeable and learning one quick rule will fix the dilemma forever! Article usage can trip up even savvy grammaticians.
AN
Use the pronoun an before a word that begins with a vowel or the sound of a vowel. (Remember that the vowels are a, e, i, o, and u.)
It is essential not to miss the key word in the rule: the SOUND of a vowel.
an apple
an octopus
an hour
In these examples, apple and octopus begin with vowels. The word hour, however, begins with the consonant H, but it sounds like the vowel O. Since we pronounce the H in hour like a vowel, use the article an.
A
Use the pronoun a before a word that begins with a consonant letter or has the SOUND of a consonant.
a ball
a towel
a university
In these examples, beach and towel begin with consonants. The word university begins with a vowel, but it has the sound of a consonant. The U in university sounds like a y in you-niversity. Therefore, use the article a. Learn more about this in Grammar I.
Just memorizing this simple rule will ensure that your article usage is correct every time!