That, Which and That

Using that instead of who when referring to people.

Using That, Which, and Who as Relative Pronouns

That, which, and who when used as relative pronouns each has a distinct function.

Which refers only to things. Who (or its forms whom and whose) refers only to people. That normally refers to things, but it may refer to a class or type of person.

Examples:

That is a book which I need for the class.

These are the books that I need for the class.

He is the man who will be teaching the class.

They are the type of people who would lie to their mothers.

They are the type of people that would lie to their mothers.

(That is OK here because it is a class or type.)