Kowa Seki (Seki Takakazu, 関 孝和) (1642? – October 24, 1708) was a Japanese mathematician who created a new mathematical notation system and used it to discover many of the theorems and theories that were being - or were shortly to be - discovered in the West, including recreating major results in calculus. He was a contemporary with Gottfried Leibniz and Isaac Newton, although he is not known to have had contact with them.

Seki was born in Fujioka in Gunma prefecture. Much of his reputation stems from the social reform he introduced in order to develop the study of mathematics in Japan and make it widely accessible.

He introduced Kanji to represent unknowns and variables in equations, and although he was obliged to confine his work to equations up to the fifth degree - his algebraic alphabet (endan-jutsu) was not suitable for general equations of the nth degree. He was able to create equations with literal coefficients of any degree and with several variables, and to solve simultaneous equations. In this way he was able to derive the equivalent of f(x), and thereby to arrive at the notion of a discriminant - a special function of the root of an equation expressible in terms of the coefficients.

Another of Seki's contributions was the rectification of the circle, i.e. the calculation of pi; he obtained a value for that was correct to the 18th decimal place.

See also

• Sangaku