In object-oriented programming, the single responsibility principle states that every class should have responsibility over a single part of the functionality provided by the software, and that responsibility should be entirely encapsulated by the class. All its services should be narrowly aligned with that responsibility.
Source: Wikipedia contributors, "Single responsibility principle," Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Single_responsibility_principle&oldid=661236643 (accessed August 3, 2015).