- Marcel Duchamp (Wikipedia)
Henri-Robert-Marcel Duchamp (UK: /ˈdjuːʃɒ̃/, US: /djuːˈʃɒ̃, djuːˈʃɑːmp/, French: [maʁsɛl dyʃɑ̃]; 28 July 1887 – 2 October 1968) was a French painter, sculptor, chess player, and writer whose work is associated with Cubism, Dada, and conceptual art. He is commonly regarded, along with Pablo Picasso and Henri Matisse, as one of the three artists who helped to define the revolutionary developments in the plastic arts in the opening decades of the 20th century, responsible for significant developments in painting and sculpture. He has had an immense impact on 20th- and 21st-century art, and a seminal influence on the development of conceptual art. By the time of World War I, he had rejected the work of many of his fellow artists (such as Henri Matisse) as “retinal”, intended only to please the eye. Instead, he wanted to use art to serve the mind.
- Natural number (Wikipedia)
In mathematics, the natural numbers are the numbers 1, 2, 3, etc., possibly including 0 as well. Some definitions, including the standard ISO 80000-2, begin the natural numbers with 0, corresponding to the non-negative integers 0, 1, 2, 3, …, whereas others start with 1, corresponding to the positive integers 1, 2, 3, … Texts that exclude zero from the natural numbers sometimes refer to the natural numbers together with zero as the whole numbers, while in other writings, that term is used instead for the integers (including negative integers). In common language, particularly in primary school education, natural numbers may be called counting numbers to intuitively exclude the negative integers and zero, and also to contrast the discreteness of counting to the continuity of measurement—a hallmark characteristic of real numbers.