Raphael asks: When should I use “a” and when should I use “an” before the different words? For example, should I say “a hour” or “an hour?” I stumble over this everytime and dont’t know if I’m getting it right, as I’m not speaking and writing English natively.
The rule states that “a” should be used before words that begin with consonants (e.g., b, c ,d) while “an” should be used before words that begin with vowels (e.g., a,e,i). Notice, however, that the usage is determined by the pronunciation and not by the spelling, as many people wrongly assume.
You should say, therefore, “an hour” (because hour begins with a vowel sound) and “a history” (because history begins with a consonant sound).
Similarly you should say “a union” even if union begins with a “u.” That is because the pronunciation begins with “yu”, which is a consonant sound.
Deciding which version you should use with abbreviations is the tricky part. First of all you need to understand if the abbreviation is pronounced as a single word or letter by letter.
While we say “a light-water reactor,” the abbreviation is “an LWR.”
Similarly, you should use “an NBC reporter” (because “NBC” is pronounced “enbisi”) and “a NATO authority” (because “NATO” begins with a “ne” sound).