A or AN?

Choose the correct option:
1) "I have to wear ____ uniform to work" 
     a) A                  b) AN


2) "He's been waiting for you for over ____ hour!"    
     a) A                   b) AN


If you chose a)A for 1, you're right! Every so often my students ask me: "But teacher, don't we have to use AN before uniform since this word begins with a vowel?!"


Careful! It's not the ortographic (written) representation of the letter that justifies the use of the indefinite articles A or AN. The phonetic (sound) quality of the first letter in a word does it, though. 

Because A X AN is taught in grammar books, people might think this is a grammar rule. Even though, u is a vowel,  its sound in the word uniform or university is of a semi-vowel: /y/.  Before semi-vowels we use the article A. So you say a unicorn, a European country, etc. We also use A before consonant-type sounds, such as A teacher, A car, etc.



The correct option in 2 is b)AN because although the word hour begins with a consonant, its pronunciation starts with a vowel-type sound.
So you say an umbrella, an egg, an uncle, an honest person, etc.



Fonte: English Pronunciation for Brazilians - The sounds of American English.