The use of "a" or "an" in a sentence.

[Anonymous]

What is the rule when using 'a' or 'an' in a sentence?

[Tdol]

A + consonant sound
An + vowel sound
(Note it is the sound, not the spelling- an egg, a European, etc)
They are both used with a singular uncountable noun that hasn't been specified.

[Maria C]

I am a spanish teacher
I will like to know hte use of " a" or "an" in a sentence.

thank you