The screw turbine is a water turbine which uses the principle of the Archimedean screw to convert the potential energy of water on an upstream level into work.
 It may be compared to the water wheel.
 The turbine consists of a rotor in the shape of an Archimedean screw which rotates in a semicircular trough.
 Water flows into the turbine and its weight presses down onto the blades of the turbine, which in turn forces the turbine to turn.
 Water flows freely off the end of the turbine into the river.
 The upper end of the screw is connected to a generator through a gearbox.
The Turn of the Screw (also known as Ghost Story: The Turn of the Screw) is a British television film based on Henry James's 1898 ghost story of the same name.
 Commissioned and produced by the BBC, it was first broadcast on 30 December 2009, on BBC One.
 The novella was adapted for the screen by Sandy Welch, and the film was directed by Tim Fywell.
 Although generally true to the tone and story of James's work, the film is set in the 1920s—in contrast to the original 1840s setting—and accentuates sexual elements that some theorists have identified in the novella.
 The film's story is told in flashbacks during consultations between the institutionalised Ann (Michelle Dockery) and Dr Fisher (Dan Stevens).
 Ann tells how she was hired by an aristocrat (Mark Umbers) to care for the orphans Miles (Josef Lindsay) and Flora (Eva Sayer).
 She is met at the children's home, Bly, by Mrs Grose (Sue Johnston), the housekeeper.
 Ann soon begins to see unknown figures around the manor, and seeks an explanation.
A differential screw is a mechanism used for making small, precise adjustments to the spacing between two objects (such as in focusing a microscope, moving the anvils of a micrometer, or positioning optics).
 A differential screw uses a spindle with two screw threads of differing leads (aka thread pitch), and possibly opposite handedness, on which two nuts move.
 As the spindle rotates, the space between the nuts changes based on the difference between the threads.
 These mechanisms allow extremely small adjustments using commonly available screws.
 A differential screw mechanism using two nuts incurs higher friction and therefore requires more torque to turn than a simple, single lead screw with an equivalent pitch.
The Turn of the Screw is a 20th-century English chamber opera composed by Benjamin Britten with a libretto by Myfanwy Piper, "wife of the artist John Piper, who had been a friend of the composer since 1935 and had provided designs for several of the operas".
 The libretto is based on the novella "The Turn of the Screw" by Henry James.
 The opera was commissioned by the Venice Biennale and given its world premiere on 14 September 1954, at the Teatro La Fenice, Venice.
 The original recording was made during that year, with the composer conducting.
A screw drive is a system used to turn a screw.
 At a minimum, it is a set of shaped cavities and protrusions on the screw head that allows torque to be applied to it.
 Usually, it also involves a mating tool, such as a screwdriver, that is used to turn it.
 The following heads are categorized based on commonality, with some of the less-common drives being classified as "tamper-resistant".
The crank machine was a device which turned a crank by hand which in turn forced four large cups or ladles through sand inside a drum, doing nothing useful.
 Male prisoners had to turn the handle 14,400 times a day, as registered on a dial.
 The warder could make the task harder by tightening an adjusting screw, hence the slang term "screw" for prison warder.
Cam out (or cam-out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount.
 Repeatedly camming out damages the screw, and possibly also the screwdriver, and should normally be avoided.
Martha, oder Der Markt zu Richmond ("Martha, or The Market at Richmond") is a "romantic comic" opera in four acts by Friedrich von Flotow set to a German libretto by Friedrich Wilhelm Riese and based on a story by Jules-Henri Vernoy de Saint-Georges.
Lead is the axial advance of a helix or screw during one complete turn (360°) The lead for a screw thread is the axial travel for a single revolution.
A screwdriver is a tool, manual or powered, for turning (driving or removing) screws.
 A typical simple screwdriver has a handle and a shaft, and a tip that the user inserts into the screw head to turn it.
 The shaft is usually made of tough steel to resist bending or twisting.
 The tip may be hardened to resist wear, treated with a dark tip coating for improved visual contrast between tip and screw—or ridged or treated for additional 'grip'.
 Handles are typically wood, metal, or plastic and usually hexagonal, square, or oval in cross-section to improve grip and prevent the tool from rolling when set down.
 Some manual screwdrivers have interchangeable tips that fit into a socket on the end of the shaft and are held in mechanically or magnetically.
 These often have a hollow handle that contains various types and sizes of tips, and a reversible ratchet action that allows multiple full turns without repositioning the tip or the user's hand.

Question: Both The Turn of the Screw and Martha are categorized as what genre?
Answer: opera