1 (one;  /ˈwʌn/ or UK /ˈwɒn/) is a number, a numeral, and the name of the glyph representing that number. It represents a single entity, the unit of counting or measurement. For example, a line segment of "unit length" is a line segment of length 1.

One, sometimes referred to as unity, is the integer before two and after zero. One is the first non-zero number in the natural numbers as well as the first odd number in the natural numbers.

Any number multiplied by one is the number, as one is the identity for multiplication. As a result, one is its own factorial, its own square, its own cube, and so on. One is also the empty product, as any number multiplied by one is itself, which produces the same result as multiplying by no numbers at all.

The glyph used today in the Western world to represent the number 1, a vertical line, often with a serif at the top and sometimes a short horizontal line at the bottom, traces its roots back to the Indians, who wrote 1 as a horizontal line, much like the Chinese character 一. The Gupta wrote it as a curved line, and the Nagari sometimes added a small circle on the left (rotated a quarter turn to the right, this 9-look-alike became the present day numeral 1 in the Gujarati and Punjabi scripts). The Nepali also rotated it to the right but kept the circle small. This eventually became the top serif in the modern numeral, but the occasional short horizontal line at the bottom probably originates from similarity with the Roman numeral Failed to parse (Missing texvc executable; please see math/README to configure.): \mathrm{I} . In some European countries (e.g., Germany), the little serif at the top is sometimes extended into a long upstroke, sometimes as long as the vertical line, which can lead to confusion with the glyph for seven in other countries. Where the 1 is written with a long upstroke, the number 7 has a horizontal stroke through the vertical line.

Alicia Augello Cook (born January 25, 1981), better known by her stage name Alicia Keys, is an American R&B singer-songwriter, record producer, and actress. Keys was raised by a single mother in the Hell's Kitchen area of Manhattan in New York City. At age seven, Keys began playing the piano. She attended Professional Performing Arts School and graduated at 16 as valedictorian. Keys released her debut album with J Records, having had previous record deals first with Columbia and then Arista Records.

Keys' debut album, Songs in A Minor, was a commercial success, selling over 12 million copies worldwide. She became the best-selling new artist and best-selling R&B artist of 2001. The album earned Keys five Grammy Awards in 2002, including Best New Artist and Song of the Year for "Fallin'". Her second studio album, The Diary of Alicia Keys, was released in 2003 and was also another success worldwide, selling eight million copies. The album garnered her an additional four Grammy Awards in 2005. Later that year, she released her first live album, Unplugged, which debuted at number one in the United States. She became the first female to have an MTV Unplugged album to debut at number one and the highest since Nirvana in 1994.

Gustav Mahler (German pronunciation: [ˈɡʊstaf ˈmaːlɐ]; 7 July 1860 – 18 May 1911) was a late-Romantic Austrian composer and one of the leading conductors of his generation. He was born in the village of Kalischt, Bohemia, in what was then the Austrian Empire, now Kaliště in the Czech Republic. Then his family moved to nearby Iglau (now Jihlava) where Mahler grew up.

As a composer, he acted as a bridge between the 19th century Austro-German tradition and the modernism of the early 20th century. While in his lifetime his status as a conductor was established beyond question, his own music gained wide popularity only after periods of relative neglect which included a ban on its performance in much of Europe during the Nazi era. After 1945 the music was discovered and championed by a new generation of listeners; Mahler then became one of the most frequently performed and recorded of all composers, a position he has sustained into the 21st century.

Born in humble circumstances, Mahler displayed his musical gifts at an early age. After graduating from the Vienna Conservatory in 1878, he held a succession of conducting posts of rising importance in the opera houses of Europe, culminating in his appointment in 1897 as director of the Vienna Court Opera (Hofoper). During his ten years in Vienna, Mahler—who had converted to Catholicism from Judaism to secure the post—experienced regular opposition and hostility from the anti-Semitic press. Nevertheless, his innovative productions and insistence on the highest performance standards ensured his reputation as one of the greatest of opera conductors, particularly as an interpreter of the stage works of Wagner and Mozart. Late in his life he was briefly director of New York's Metropolitan Opera and the New York Philharmonic.