I'm confused in an or a , I mean which time we will use " an " or in which time will we use " a ". I'm using them what I feel like yeah my sentence is correct n all.

consonants= a vowels= an word having Vowel sound but starts with consonant= An honest word having consonant sound but starts with Vowel= a university

A, An and The - These three are called articles. A will be used if the next word starts with a consonant sound. For example. This is a table. I have a bicycle. AND A will be used if the next word starts with a vovel sound. For example. I see an alligator snapping at an otter. He has an airplane.