  Steganography is the practice of concealing a message within some other
carrier or cover message. It is used to allow the sending of hidden information
through communication channels where third parties would only be aware of the
explicit information in the carrier message. With the growth of internet
surveillance and the increased need for secret communication, steganography
systems continue to find new applications. In semantic steganography, the
redundancies in the semantics of a language are used to send a text
steganographic message. In this article we go over the concepts behind semantic
steganography and propose a hierarchy for classifying systems within the
context of text steganography and steganography in general. After laying this
groundwork we list systems for semantic steganography that have been published
in the past and review their properties. Finally, we comment on and briefly
compare the described systems.
