Idrees Ahmad Khan2025-11-172025978-93-6884-936-0http://136.232.12.194:4000/handle/123456789/1549In Advanced Studies in Mathematics and Statistics Editor: Mobin Ahmad"In this chapter, we have defined some basic ideas about the Approximation theory with their properties and applications. The approximation theory has a close relationship with other branches of mathematics (like Fourier analysis). Existence of such a relationship is explained by the fact that many important problems of the approximation theory are formulated."en-USMATHEMATICSBook chapter