Tear

Tears, or lachrymatory secretions, were the liquids secreted from an individuals' eyes during the act of crying. This could be caused by stress or pain, (COMIC: The Infinite Astronaut) as well as grief, guilt, anger and panic. (AUDIO: Harvest of the Sycorax)

The automatic visor washers Carl Readon installed in the robot, Robbie allowed him to produce tears. (COMIC: Doctor Who and the Robot)