We've all been taught in primary school how we're supposed to use 'an' instead of 'a' when we talk about an object whose name starts with a vowel, in its singular form.
-> An Apple
-> An Ostrich
-> An Elephant
But when we refer to one university, universe or even adjectives like useless, we use 'a' instead of 'an'.
-> A University
-> A Useless Boy
-> A Unique sight
Why is that so ? I get the fact that we use 'an' for words which start with consonants occasionally, for words like 'Hour','Honor', because the 'H' is silent. But what of the exceptions in the case of words starting with A,E,I,O,U ? Or is the just for certain words that start with 'U' ?