In geometry, a nonagon  /ˈnɒnəɡɒn/ (or enneagon /ˈɛniːəɡɒn/) is a nine-sided polygon.

The name "nonagon" is a prefix hybrid formation, from Latin (nonus, "ninth" + gonon), used equivalently, attested already in the 16th century in French nonogone and in English from the 17th century. The name "enneagon" comes from Greek enneagonon (εννεα, "nine" + γωνον (from γωνία = "corner")), and is arguably more correct, though somewhat less common.

A regular nonagon has internal angles of 140°. The area of a regular nonagon of side length a is given by

Although a regular nonagon is not constructible with compass and straightedge there are methods of construction that produce very close approximations.

Below is a close approximation of a regular nonagon. The approximate angle error is given in the animation.

The K₉complete graph is often drawn as a regular enneagon with all 36 edges connected. This graph also represents an orthographic projection of the 9 vertices and 36 edges of the 8-simplex. Three other rectified forms also project inside of a regular enneagon:

Erica Abi Wright (born February 26, 1971), better known by her stage name Erykah Badu /ˈɛrɨkə bɑːˈduː/, is a Grammy Award-winning American singer-songwriter, record producer, activist and actress. Her work includes elements from R&B, hip hop and jazz. She is best known for her role in the rise of the neo soul sub-genre, and for her eccentric, cerebral musical stylings and sense of fashion. She is known as the "First Lady of Neo-Soul" or the "Queen of Neo-Soul".

Early in her career, Badu was recognizable for wearing very large and colorful headwraps. For her musical sensibilities, she has often been compared to jazz great Billie Holiday. She was a core member of the Soulquarians, and is also an actress having appeared in a number of films playing a range of supporting roles in movies such as Blues Brothers 2000, The Cider House Rules and House of D. She also speaks at length in the documentary Before the Music Dies.

Erykah Badu was born Erica Abi Wright in Dallas, Texas, on February 26, 1971. Her mother raised her and her brother and sister alone; their father, William Wright, Jr., had deserted the family early in their lives. To provide for her family, the children's grandmother often helped looking after them while Erykah's mother, Kolleen Maria Gipson (Wright), performed as an actress in theatrical productions. Influenced by her mother, Erykah had her first taste of show business at the age of 4, singing and dancing with her mother at the Dallas Theatre Centre. Erykah Badu was the owner of Focal point in Dallas, Texas.