The letter c makes a hard sound (like k) in some words, but a soft sound (like s) in others. For example:
city (soft c)
cat (hard c)
The way we pronounce the letter c in a word usually depends on the letter that comes straight after the c.
If the next letter is e, i or y, the c is usually soft.
cent cinema cylinder
If the next letter is a, o or u, it is usually hard.
cake conker cup