A graph is a visual representation of data or a mathematical function, showing relationships between variables.
Graphs display mathematical relationships on coordinate axes. The Cartesian coordinate system uses x (horizontal) and y (vertical) axes. Common graph types include line graphs, bar charts, scatter plots, and pie charts. In functions, the graph shows all points (x, f(x)). The slope, intercepts, and shape of a graph reveal important properties of the function or data. Graphs are used in every scientific and analytical field.
The coordinate system was developed by Renรฉ Descartes in the 17th century, revolutionizing mathematics by linking algebra and geometry. William Playfair invented bar charts and line graphs in the 18th century. The field of graph theory, studying networks of vertices and edges, was founded by Leonhard Euler's solution to the Kรถnigsberg Bridge problem in 1736.