Someone finally noticed! It's not mistake, though. Long story short, I made it as a bit of a joke on how ridiculous the English language can be: we're told that "a" before a vowel becomes "an," but it sounds wrong with words that start with 'uni-' because it doesn't apply there (...or with 'an hour and an honor, and depending your accent, it can be either 'a herb' or 'an herb)...we have so many exceptions, no wonder even native speakers find spelling hard!
Well, it isn't really exceptions - the rule is "a" in front of consonant sounds and "an" in front of vowel sounds - not the written consonants and vowels. "Hour" and "honor" both start with a silent "h" and thus the first sound is a vowel, "unicorn" on the other hand starts with a consonant sound (which could be written as "y" in English - such as in "you") and therefore "a" is the correct article to use here. No exceptions, just different rules than what you've learned.
Yeah, exactly what RaneSchjtt said. You only place 'an' before a word that sounds like it begins with a vowel. Not merely because it is a vowel letter. Take your username for instance. Unicorn is pronounced 'you-nee-corn' not 'uh-nee-corn'. So in proper text, we would write in a sentence "the man had bought a unicorn". The same goes with a word like "utopia". It is pronounced as "you-toe-pia" so we say "a utopia". In your examples, "hour", "honour", and "herb", the h is silent and thus the vowel sound of the o is what the word begins with. That is why to be grammatically correct, you need to put a 'an' before those types of words. :) I know its been a year, but this post can be for anyone else having problems with English despite being in the Dutch section and considering 4 people agreed with you.
Oh, I just meant that I intended to use the wrong "a/an" as a joke (and because AUnicorn was taken).
I know it's incorrect because you go by the first sound in the following word, but none of the English classes I had as a native ever really went in depth on phonology--they just said "vowels get 'an,' consonants get 'a,' and 'hour', ' honor' and 'herb' are exceptions."
And I imagine it's even more difficult for ESL learners--"uni" can get two different pronunciations and take either a/an: it's a when it's uni- as a Latinate prefix for "one" (uni + corn - "one-horn", uni + verse "[everything] combined into one; the whole"; "uni + t", apparently a modification of unus under the influence of "digit") and an when it's un- + i... (un + important, un + invited). Easy enough when you grow up learning it, but how are you going to know which "uni" it is when you're just starting to learn the language?
Never thought about trying to find the rules behind it until you asked!
I think this article can help you: http://www.dutchgrammar.com/en/?n=NounsAndArticles.11