Seki's calculus is a mathematical system developed by the Japanese mathematician Seki Takakazu in the 17th century. It focuses on the manipulation of numbers and geometric figures, particularly in the context of solving problems related to areas and volumes. Seki's work laid the groundwork for later developments in calculus and algebra. One of the key features of Seki's calculus is its use of a method similar to infinitesimals, which allows for the approximation of quantities. This approach was innovative for its time and contributed to the evolution of mathematical thought in Japan, influencing later mathematicians and the study of mathematics in the region.