th和tch在读音上有什么区别

th：
(1) th位于词首时,可以从词性上判别其应有的读音.在名词、动词、形容词和数词中th发清辅音.如：thing,theatre,thunder,thermos,Thursday,theory,theme,throat,thread,think,thank,thrive,thicken,thirteen,thirty,third,thousand,thick,thirsty,thoughtful,thorough 在代词和一些功能词中th发浊辅音.如：them,their,theirs,there,the,than,then,though,thus,therefore,they.只有介词through是个例外.
(2) th位于词尾（或音节之尾）时,其读音多数是清辅音,如：bath,breath,tooth,等.只有在少数单词中,如：with,smooth 中读浊音.
(3) th在词中并且后面接er时,或者最后一个字母是不发音的e时,通常也发浊辅音.例如：feather,weather,whether,leather,further,father,bathe,breathe,southern,northern,either等.在其他情况下发清辅音.例如：author,faithful,method,nothing,anything,healthy,wealthy.

tch：发/tʃ/的音。就是中文“吃”[chi]裏面的[ch]