Ramsey

Ramsey is a name used as both a surname and a place name. It has English origins, deriving from multiple places named Ramsey in England, and spread to other parts of the world through migration and settlement.

Ramsey's theorem, named after the British mathematician Frank P. Ramsey (1903–1930), is a cornerstone of Ramsey theory in combinatorics. The classic two-color version states that for any positive integers r and s, there exists a minimum n such that every red/blue coloring of the edges of a complete graph on n vertices contains a red K_r or a blue K_s (a monochromatic complete subgraph). The result generalizes to more colors and to hypergraphs, and Ramsey theory studies unavoidable patterns that emerge in large structures.

Geographically, Ramsey occurs as a place name in several countries. The Isle of Man has a coastal village named Ramsey. In the United States, Ramsey is the name of towns and counties, including Ramsey, New Jersey, and Ramsey County in Minnesota (named for Alexander Ramsey, a 19th-century American politician).

People bearing the surname Ramsey include Frank P. Ramsey, a mathematician and philosopher who formulated Ramsey's theorem, and Dave Ramsey, an American author and radio host known for advising on personal finance.