A sign system is a key concept in semiotics and is used to refer to any system of signs and relations between signs. The term language is frequently used as a synonym for a sign-system. However, the term sign-system is considered preferable to the term language for a number of reasons. First, the use of the term language tends to carry with it connotations of human language, particularly human spoken language. Human spoken language is only one example of a sign-system, albeit probably one of the most complex sign-systems known. Traffic signs, art, and fashion are all examples of sign systems.