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.
Twenty-one, XXI or 21 may refer to:
- 21 (number)
- One of the years 21 BC, AD 21, 1921, 2021
Fencing is a combat sport that features sword fighting. It consists of three primary disciplines: foil, épée, and sabre (also spelled saber), each with its own blade and set of rules. Most competitive fencers specialise in one of these disciplines. The modern sport gained prominence near the end of the 19th century, evolving from historical European swordsmanship. The Italian school altered the historical European martial art of classical fencing, and the French school later refined that system. Scoring points in a fencing competition is done by making contact with the opponent with one's sword.
The 1904 Olympic Games featured a fourth discipline of fencing known as singlestick, but it was dropped after that year and is not a part of modern fencing. Competitive fencing was one of the first sports to be featured in the Olympics and, along with athletics, cycling, swimming, and gymnastics, has been featured in every modern Olympics.
Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–750 nanometres. It is a primary color in the RGB color model and a secondary color (made from magenta and yellow) in the CMYK color model, and is the complementary color of cyan. Reds range from the brilliant yellow-tinged scarlet and vermillion to bluish-red crimson, and vary in shade from the pale red pink to the dark red burgundy.
Red pigment made from ochre was one of the first colors used in prehistoric art. The Ancient Egyptians and Mayans colored their faces red in ceremonies; Roman generals had their bodies colored red to celebrate victories. It was also an important color in China, where it was used to color early pottery and later the gates and walls of palaces.: 60–61 In the Renaissance, the brilliant red costumes for the nobility and wealthy were dyed with kermes and cochineal. The 19th century brought the introduction of the first synthetic red dyes, which replaced the traditional dyes. Red became a symbolic color of communism and socialism; Soviet Russia adopted a red flag following the Bolshevik Revolution in 1917. The Soviet red banner would subsequently be used throughout the entire history of the Soviet Union. China adopted its own red flag following the Chinese Communist Revolution. A red flag was also adopted by North Vietnam in 1954, and by all of Vietnam in 1975.
Since red is the color of blood, it has historically been associated with sacrifice, danger, and courage. Modern surveys in Europe and the United States show red is also the color most commonly associated with heat, activity, passion, sexuality, anger, love, and joy. In China, India, and many other Asian countries it is the color symbolizing happiness and good fortune.: 39–63
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