Maurits Cornelis Escher (Dutch pronunciation: [ˈmʌurɪt͡s kɔrˈneːlɪs ˈɛʃər]; 17 June 1898 – 27 March 1972) was a Dutch graphic artist who made mathematically-inspired woodcuts, lithographs, and mezzotints. Despite wide popular interest, Escher was for long somewhat neglected in the art world; even in his native Netherlands; he was 70 before a retrospective exhibition was held. In the twenty-first century, he became more widely appreciated, with exhibitions across the world. His work features mathematical objects and operations including impossible objects, explorations of infinity, reflection, symmetry, perspective, truncated and stellated polyhedra, hyperbolic geometry, and tessellations. Although Escher believed he had no mathematical ability, he interacted with the mathematicians George Pólya, Roger Penrose, Harold Coxeter and crystallographer Friedrich Haag, and conducted his own research into tessellation. Early in his career, he drew inspiration from nature, making studies of insects, landscapes, and plants such as lichens, all of which he used as details in his artworks. He traveled in Italy and Spain, sketching buildings, townscapes, architecture and the tilings of the Alhambra and the Mezquita of Cordoba, and became steadily more interested in their mathematical structure. Escher's art became well known among scientists and mathematicians, and in popular culture, especially after it was featured by Martin Gardner in his April 1966 Mathematical Games column in Scientific American. Apart from being used in a variety of technical papers, his work has appeared on the covers of many books and albums. He was one of the major inspirations of Douglas Hofstadter's Pulitzer Prize-winning 1979 book Gödel, Escher, Bach.

There are numerous references to famous Dutch painter M.C. Escher, in popular culture.

The Carro Armato M15/42 was the last Italian medium tank produced during World War II. It was based on the earlier M13/40 and M14/41 medium tanks, and was built with the lessons from the North African Campaign in mind. The tank was meant to be a stopgap until the heavier P26/40 tank could be produced in numbers. It did not serve in North Africa, the theatre in which it was intended to operate, but served in Italy and in Yugoslavia with the German Wehrmacht.

The M4 Sherman, officially Medium Tank, M4, was the most widely used medium tank by the United States and Western Allies in World War II. The M4 Sherman proved to be reliable, relatively cheap to produce, and available in great numbers. Thousands were distributed through the Lend-Lease program to the British Commonwealth and Soviet Union. The tank was named by the British for the American Civil War general William Tecumseh Sherman. The M4 Sherman evolved from the M3 Medium Tank, which had its main armament in a side sponson mount. The M4 retained much of the previous mechanical design, but put the main 75 mm gun in a fully traversing turret. One feature, a one-axis gyrostabilizer, was not precise enough to allow firing when moving but did help keep the reticle on target, so that when the tank did stop to fire, the gun would be aimed in roughly the right direction. The designers stressed mechanical reliability, ease of production and maintenance, durability, standardization of parts and ammunition in a limited number of variants, and moderate size and weight. These factors, combined with the Sherman's then-superior armor and armament, outclassed German light and medium tanks fielded in 1939–42. The M4 went on to be produced in large numbers. It spearheaded many offensives by the Western Allies after 1942. When the M4 tank went into combat in North Africa with the British Army at El Alamein in late 1942, it increased the advantage of Allied armor over Axis armor and was superior to the lighter German and Italian tank designs. For this reason, the US Army believed that the M4 would be adequate to win the war, and relatively little pressure was initially exerted for further tank development. Logistical and transport restrictions, such as limitations imposed by roads, ports, and bridges, also complicated the introduction of a more capable but heavier tank. Tank destroyer battalions using vehicles built on the M4 hull and chassis, but with open-topped turrets and more potent high-velocity guns, also entered widespread use in the Allied armies. Even by 1944, most M4 Shermans kept their dual purpose 75 mm gun. By then, the M4 was inferior in firepower and armor to increasing numbers of German heavy tanks, but was able to fight on with the help of numerical superiority, greater mechanical reliability, better logistical support, and support from growing numbers of fighter-bombers and artillery pieces. Some Shermans were produced with a more capable gun, the 76 mm gun M1, or refitted with an Ordnance QF 17-pounder by the British (the Sherman Firefly). The relative ease of production allowed large numbers of the M4 to be manufactured, and significant investment in tank recovery and repair units allowed disabled vehicles to be repaired and returned to service quickly. These factors combined to give the Allies numerical superiority in most battles, and many infantry divisions were provided with M4s and tank destroyers.After World War II, the Sherman, particularly the many improved and upgraded versions, continued to see combat service in many conflicts around the world, including the UN forces in the Korean War, with Israel in the Arab–Israeli wars, briefly with South Vietnam in the Vietnam War, and on both sides of the Indo-Pakistani War of 1965.

A mace is a blunt weapon, a type of club or virge that uses a heavy head on the end of a handle to deliver powerful blows. A mace typically consists of a strong, heavy, wooden or metal shaft, often reinforced with metal, featuring a head made of stone, copper, bronze, iron, or steel. The head of a military mace can be shaped with flanges or knobs to allow greater penetration of plate armour. The length of maces can vary considerably. The maces of foot soldiers were usually quite short (two or three feet, or seventy to ninety centimetres). The maces of cavalrymen were longer and thus better suited for blows delivered from horseback. Two-handed maces could be even larger. Maces are rarely used today for actual combat, but a large number of government bodies (for instance, the British House of Commons and the U.S. Congress), universities and other institutions have ceremonial maces and continue to display them as symbols of authority. They are often paraded in academic, parliamentary or civic rituals and processions.

The machete (Portuguese: machete de braga) is a small stringed instrument from Madeira, Portugal. The instrument has four metal strings, in contrast to its slightly larger cousin, the machete de rajão, which has five metal strings. Historians believe the machete was introduced in Madeira as Braguinha from Braga, and it is the immediate predecessor of the ukulele, being introduced to Hawaii by Portuguese immigrants in the late 19th century.

A machine is a tool containing one or more parts that transforms energy. Machines are usually powered by chemical, thermal, or electrical means, and are often motorized. Historically, a power tool also required moving parts to classify as a machine. However, the advent of electronics has led to the development of power tools without moving parts that are considered machines. A simple machine is a device that simply transforms the direction or magnitude of a force, but a large number of more complex machines exist. Examples include vehicles, electronic systems, molecular machines, computers, television, and radio.

Machine element refers to an elementary component of a machine. These elements consist of three basic types: structural components such as frame members, bearings, axles, splines, fasteners, seals, and lubricants, mechanisms that control movement in various ways such as gear trains, belt or chain drives, linkages, cam and follower systems, including brakes and clutches, and control components such as buttons, switches, indicators, sensors, actuators and computer controllers.While generally not considered to be a machine element, the shape, texture and color of covers are an important part of a machine that provide a styling and operational interface between the mechanical components of a machine and its users. Machine elements are basic mechanical parts and features used as the building blocks of most machines. Most are standardized to common sizes, but customs are also common for specialized applications.Machine elements may be features of a part (such as screw threads or integral plain bearings) or they may be discrete parts in and of themselves such as wheels, axles, pulleys, rolling-element bearings, or gears. All of the simple machines may be described as machine elements, and many machine elements incorporate concepts of one or more simple machines. For example, a leadscrew incorporates a screw thread, which is an inclined plane wrapped around a cylinder. Many mechanical design, invention, and engineering tasks involve a knowledge of various machine elements and an intelligent and creative combining of these elements into a component or assembly that fills a need (serves an application).

A forming press, commonly shortened to press, is a machine tool that changes the shape of a workpiece by the application of pressure. Presses can be classified according to their mechanism: hydraulic, mechanical, pneumatic; their function: forging presses, stamping presses, press brakes, punch press, etc. their structure, e.g. Knuckle-joint press, screw press their controllability: conventional vs. servo-presses

A machine tool is a machine for shaping or machining metal or other rigid materials, usually by cutting, boring, grinding, shearing, or other forms of deformation. Machine tools employ some sort of tool that does the cutting or shaping. All machine tools have some means of constraining the workpiece and provide a guided movement of the parts of the machine. Thus the relative movement between the workpiece and the cutting tool (which is called the toolpath) is controlled or constrained by the machine to at least some extent, rather than being entirely "offhand" or "freehand". The precise definition of the term machine tool varies among users, as discussed below. While all machine tools are "machines that help people to make things", not all factory machines are machine tools. Today machine tools are typically powered other than by human muscle (e.g., electrically, hydraulically, or via line shaft), used to make manufactured parts (components) in various ways that include cutting or certain other kinds of deformation. With their inherent precision, machine tools enabled the economical production of interchangeable parts.