虽然汉语说周三是一天,但英语一般说所有的周三。所以如果是泛指每个周三都喜欢,则用Wednesdays are my favorite days.
My favorite day is 星期三的单词(好吧,我忘记咋写了)
Wednesday is my favorite day.
Every Wednesday is my favorite day.
My favourite day is Thursday.或者是Thursday are my favouriteday.