有读者问： 请问that which与连接代词what有什么区别？
二者同义，都意谓“所……的事物”。其语法功用也一样，皆用以引导一名词性从句。二者的区别在于what是一通用之词，如：
(1)What he really needs is a nice cup of tea.
(2)A computer can only do what you have programmed it to do.
(3)The meeting was put off, which was exactly what we wanted.
that which则只用于很正式的文体中，如：
(4)That which you bade me do I did.
(5)That which is most highly valued in the tribe is valour.
(6)That which upsets me most is his manner.
(7)He always does that which the hour demands, not that which he would fain do.
(8)The difference between “appropriate” and “suitable” is that “appropriate” is that which peculiarly fits or suits the general character, or some property or peculiarity of a thing or person with which it is associated.
有的语法家认为that which已属古旧，这从上述例（7）可明显地看出来。
