The most common sound a cat makes is Miaow.

They can also purr. They do this when breathing both in and out.

This sound is like "r r r r r rrrr r r r r r" when they breathe in, and when they breath out, they just reverse it, and make "r r r r r rrrr r r r r r".

Some times cats complain: "Meeeooooow"

They can also be angry: "Meowww", "fshhhhh", "fiisssssshhh"

When they say hello: "Miaow"

When they are hungry: "Miaoow"

When they are hopeful: "r r r r r rrr r r r r r" and reverse "r r r r r rrr r r r r r"

When they are utterly happy: "r r r r r rr r r r r r" and reverse "r r r r r rrrrrr r r r r r"

Note: This cat-dictionary is not complete.