There are many possible definitions about what Remote Sensing actually is.
Here's a collection of quotes.


F.F. Sabins in his book "Remote sensing: principles and interpretation" defines it as follows:


The United Nations in their annex Principles Relating to Remote Sensing of the Earth from Space defines it as:
(this definition is part of the General Assembly Resolutions and International Treaties Pertaining to the Peaceful Uses of Outer Space)


Lillesand and Kiefer in their book "Remote Sensing and Image Interpretation" even define it as an art:


Probably the broadest definition is given by Charles Elachi in "Introduction to the Physics and Techniques of Remote Sensing":


The CCRS had this in their Remote Sensing Glossary:


And on and on.