The letter c is not a reliable letter in terms of the sound it makes because it can represent so many different sounds. It makes both a hard and soft sound. The hard /k/ as represented in the words cat and cake is the most common pronunciation. The hard sound is usually made by c when it precedes the vowels a, o, or u. The letter c is also usually hard when followed by a consonant, as in the cl and cr in the words clam and cream. The letter c makes a soft sound like /s/ when followed by i (circus, circle, cigar), y (cycle, cyst), and e (center, cell, cereal). It is also usually soft in the final position when followed by silent e (race, nice). The c is sometimes both hard and soft when doubled in words like succeed. When doubled in words like occupy, one c is silent. If c comes before e or i, it can make a /sh/ sound, as in words like ocean, racial, and social.
The /k/ sound is also commonly represented by the letter k (kite) and the digraph ck (tack).