(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。 试读下列单词: mother, father, another, brother, health, wealth