When a word starts with an “s”, do you use “a” or “an ...

u201csu201d is a consonant, u201canu201d is only used before vowels. The reason for this is phonetic. We do not like the way u201ca appleu201d (for example) sounds to the ear, so we add a consonant (in this case u201cnu201d) to make it sound smoother and more flowing.
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