  As a cornerstone of functional analysis, Hahn Banach theorem constitutes an
indispensable tool of modern analysis where its impact extends beyond the
frontiers of linear functional analysis into several other domains of
mathematics, including complex analysis, partial differential equations and
ergodic theory besides many more. The paper is an attempt to draw attention to
certain applications of the Hahn Banach theorem which are less familiar to the
mathematical community, apart from highlighting certain aspects of the Hahn
Banach phenomena which have spurred intense research activity over the past few
years, especially involving operator analogues and nonlinear variants of this
theorem.
