Proceedings of the Seminar on Functional Analysis . Issue 3-4”, edited by the famous mathematician Mikhail Alexandrovich Krasnoselsky, is a unique publication that will become a real treasure for everyone who is interested in modern trends in the field of functional analysis. This specialized edition, consisting of two issues, covers a wide range of topics related to this important branch of mathematics, and offers readers a deep immersion into the world of abstract concepts and theories. Functional analysis is the field of mathematics that studies functionals and infinite-dimensional vector spaces. In this context, the book is a collection of papers prepared by the participants of the seminar, which gathers leading scientists and researchers in this field. Each issue contains articles that cover both classical and contemporary aspects of functional analysis, including, but not limited to, topics such as operator theory, spectral theory, topological vector spaces, and much more. The book will be of particular interest to students, graduate students and teachers involved in mathematics, as well as professional mathematicians who are looking for new ideas and approaches in their research work. If you are passionate about mathematics and want to deepen your knowledge in functional analysis, then this publication will become an indispensable source of information and inspiration for you. It will also be useful to those interested in the applied aspects of mathematics, as functional analysis finds application in various fields such as physics, economics, and engineering. One of the main topics raised in the book is the interaction between theory and practice. The authors aim to show how abstract mathematical concepts can be applied to solve real-world problems. This makes the book particularly relevant in light of the current challenges facing the scientific community. Readers will be able to see how functional analysis can serve as a powerful tool for understanding complex systems and processes. The style of Mikhail Alexandrovich Krasnoselsky, as an editor, is distinguished by clarity and accessibility, which makes even the most complex topics understandable to a wide audience. Krasnoselsky is the author of many works, among which such famous books as