The document discusses the passive causative construction in linguistics. It defines the passive causative as using a causative verb like have, get, make, or let to indicate that one person caused a second person to do something. Examples are given of active sentences being changed to their passive causative form, such as "I tell him to type the letter" becoming "I let the letter typed by him." The passive causative is used to ask, tell, or order something to be done by someone.