ㄗ
Sounds kind of like "ds" in "bids", but voiceless.
ㄗˋㄐㄧˇ
oneself
自己
ㄗㄞˋㄐㄧㄢˋ
goodbye
再见
ㄘ
Sounds kind of like "ts" in "cats".
ㄘˊ
word
词
ㄘㄜˋㄙㄨㄛˇ
bathroom
厕所
ㄙ
Sounds like "s" in "sick".
ㄙˋ
four
四
ㄙㄢ
three
三
Single-syllable audio courtesy of the AllSet Learning Chinese Pronunciation Wiki, used with permission.
HSK word audio courtesy of Audio-cmn. (CC BY-SA 3.0)