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

u201 cs u201 d is a consonant, u201 can u201 d is just used before vowels. We do not like the method u201 ca apple u201 d (for example) sounds to the ear, so we add a consonant (in this case u201 cn u201 d) to make it sound smoother and more flowing.

https://businessadministrationcertification.com/when-a-word-starts-with-an-s-do-you-use-a-or-an/