The authors explain the Fourier transform and its applications, especially in signal and system theory. Based on their many years of teaching experience, they aim at helping especially STEM (science, technology, engineering, and mathematics) students as well as graduated professionals to better understand the subject. The authors also point out the importance of a deeper understanding, as all modern digital technologies such as sound and image recording and storage, radio and television, mobile telephony, signal transmission for the Internet, modern control techniques for vehicles or aircrafts - are largely based on the Fourier transform. This Springer essential is a translation of the original German 1st edition essentials, Fourier-Transformation zur Signal- und Systembeschreibung by Jörg Lange and Tatjana Lange, published by Springer Fachmedien Wiesbaden GmbH, part of Springer Nature in 2019. The translation was done with the help of artificial intelligence (machine translation by the service DeepL.com). A subsequent human revision was done primarily in terms of content, so that the book will read stylistically differently from a conventional translation. Springer Nature works continuously to further the development of tools for the production of books and on the related technologies to support the authors. The Content Sine and cosine as building blocks for periodic functions; Fourier series and Fourier integral Fourier transform of standard signals, properties and approximate relationships Fourier transform for describing signals and systems and its application to stochastic signals Optimal receive filter (Wiener filter) The Authors Prof. Dr.-Ing. habil. Jörg Lange held a leading position in the development area of mobile communications in a large technology company. Prof. Dr.-Ing. Tatjana Lange taught control systems engineering at Merseburg University of Applied Sciences and is still active in research in the area of classification and cluster analysis.