Tarter 40 gal. Versa Oval Galvanized Steel Tank, 2 ft. x 1 ft. x 4 ft., Spigot Included

1 (one, unit, unity) is a number, numeral, and glyph. It is the first and smallest positive integer of the infinite sequence of natural numbers. This fundamental property has led to its unique uses in other fields, ranging from science to sports, where it commonly denotes the first, leading, or top thing in a group. 1 is the unit of counting or measurement, a determiner for singular nouns, and a gender-neutral pronoun. Historically, the representation of 1 evolved from ancient Sumerian and Babylonian symbols to the modern Arabic numeral.

In mathematics, 1 is the multiplicative identity, meaning that any number multiplied by 1 equals the same number. 1 is by convention not considered a prime number. In digital technology, 1 represents the "on" state in binary code, the foundation of computing. Philosophically, 1 symbolizes the ultimate reality or source of existence in various traditions.

2 (two) is a number, numeral and digit. It is the natural number following 1 and preceding 3. It is the smallest and the only even prime number.

Because it forms the basis of a duality, it has religious and spiritual significance in many cultures.

4 (four) is a number, numeral and digit. It is the natural number following 3 and preceding 5. It is a square number, the smallest semiprime and composite number, and is considered unlucky in many East Asian cultures.

40 or forty commonly refers to:

• 40 (number)
• one of the years 40 BC, AD 40, 1940, 2040

40 or forty may also refer to:

An oval (from Latin ovum 'egg') is a closed curve in a plane which resembles the outline of an egg. The term is not very specific, but in some areas (projective geometry, technical drawing, etc.) it is given a more precise definition, which may include either one or two axes of symmetry of an ellipse. In common English, the term is used in a broader sense: any shape which reminds one of an egg. The three-dimensional version of an oval is called an ovoid.

Steel is an alloy of iron and carbon with improved strength and fracture resistance compared to other forms of iron. Because of its high tensile strength and low cost, steel is one of the most commonly manufactured materials in the world. Steel is used in buildings, as concrete reinforcing rods, in bridges, infrastructure, tools, ships, trains, cars, bicycles, machines, electrical appliances, furniture, and weapons.

Iron is always the main element in steel, but many other elements may be present or added. Stainless steels, which are resistant to corrosion and oxidation, typically need an additional 11% chromium.

Iron is the base metal of steel. Depending on the temperature, it can take two crystalline forms (allotropic forms): body-centred cubic and face-centred cubic. The interaction of the allotropes of iron with the alloying elements, primarily carbon, gives steel and cast iron their range of unique properties. In pure iron, the crystal structure has relatively little resistance to the iron atoms slipping past one another, and so pure iron is quite ductile, or soft and easily formed. In steel, small amounts of carbon, other elements, and inclusions within the iron act as hardening agents that prevent the movement of dislocations.

The carbon in typical steel alloys may contribute up to 2.14% of its weight. Varying the amount of carbon and many other alloying elements, as well as controlling their chemical and physical makeup in the final steel (either as solute elements, or as precipitated phases), impedes the movement of the dislocations that make pure iron ductile, and thus controls and enhances its qualities. These qualities include the hardness, quenching behaviour, need for annealing, tempering behaviour, yield strength, and tensile strength of the resulting steel. The increase in steel's strength compared to pure iron is possible only by reducing iron's ductility.

Steel was produced in bloomery furnaces for thousands of years, but its large-scale, industrial use began only after more efficient production methods were devised in the 17th century, with the introduction of the blast furnace and production of crucible steel. This was followed by the Bessemer process in England in the mid-19th century, and then by the open-hearth furnace. With the invention of the Bessemer process, a new era of mass-produced steel began. Mild steel replaced wrought iron. The German states were the major steel producers in Europe in the 19th century. American steel production was centred in Pittsburgh, Bethlehem, Pennsylvania, and Cleveland until the late 20th century. Currently, world steel production is centered in China, which produced 54% of the world's steel in 2023.

Further refinements in the process, such as basic oxygen steelmaking (BOS), largely replaced earlier methods by further lowering the cost of production and increasing the quality of the final product. Today more than 1.6 billion tons of steel is produced annually. Modern steel is generally identified by various grades defined by assorted standards organizations. The modern steel industry is one of the largest manufacturing industries in the world, but also one of the most energy and greenhouse gas emission intense industries, contributing 8% of global emissions. However, steel is also very reusable: it is one of the world's most-recycled materials, with a recycling rate of over 60% globally.

A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and battlefield mobility provided by tracks and a powerful engine; their main armament is often mounted within a turret. They are a mainstay of modern 20th and 21st century ground forces and a key part of combined arms combat.

Modern tanks are versatile mobile land weapons platforms whose main armament is a large-caliber tank gun mounted in a rotating gun turret, supplemented by machine guns or other ranged weapons such as anti-tank guided missiles or rocket launchers. They have heavy vehicle armour which provides protection for the crew, the vehicle's munition storage, fuel tank and propulsion systems. The use of tracks rather than wheels provides improved operational mobility which allows the tank to overcome rugged terrain and adverse conditions such as mud and ice/snow better than wheeled vehicles, and thus be more flexibly positioned at advantageous locations on the battlefield. These features enable the tank to perform in a variety of intense combat situations, simultaneously both offensively (with direct fire from their powerful main gun) and defensively (as fire support and defilade for friendly troops due to the near invulnerability to common infantry small arms and good resistance against heavier weapons, although anti-tank weapons used in 2022, some of them man-portable, have demonstrated the ability to destroy older generations of tanks with single shots), all while maintaining the mobility needed to exploit changing tactical situations. Fully integrating tanks into modern military forces spawned a new era of combat, armoured warfare.

Until the invention of the main battle tank, tanks were typically categorized either by weight class (light, medium, heavy or superheavy tanks) or doctrinal purpose (breakthrough-, cavalry-, infantry-, cruiser-, or reconnaissance tanks). Some are larger and more thickly armoured and with large guns, while others are smaller, lightly armoured, and equipped with a smaller caliber and lighter gun. These smaller tanks move over terrain with speed and agility and can perform a reconnaissance role in addition to engaging hostile targets. The smaller, faster tank would not normally engage in battle with a larger, heavily armoured tank, except during a surprise flanking manoeuvre.

X, or x, is the twenty-fourth letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ex (pronounced ), plural exes.