Which leads us to "a" and "an". The "n" is added when the next word starts with a vowel, if I'm not mistaken.
nowt is simples, take H, some words starting with H use an (an hour) whilst others don't (a horse).
In fact the proper rule* is if the next word starts with the
sound of a vowel, use 'an'.
> 'Hour' starts with an "a" sound, as in apple, and 'a' is a vowel, thus "an hour".
> 'Horse' starts with an "h" sound, as in hop, hip and happy, and 'h' is a consonant, thus "a horse".
> 'X-ray' starts with an "e" sound, as in elephant, and 'e' is a vowel, thus "an X-ray"
> 'Uniform" starts with a "y" sound, as in yank, and 'y' is a consonant, thus "a uniform".
* Strictly speaking English, unlike French, does not have "rules", but rather
conventions and
common usage.