The semiotic square, also known as the Greimas square, is a tool used in structural analysis of the relationships between semiotic signs through the opposition of concepts, such as feminine-masculine or beautiful-ugly, and of extending the relevant ontology.
Semiotic square
Semiotics is the systematic study of sign processes and the communication of meaning. In semiotics, a sign is defined as anything that communicates intentional and unintentional meaning or feelings to the sign's interpreter.
Color-coding hot- and cold-water faucets (taps) is common in many cultures but, as this example shows, the coding may be rendered meaningless because of context. The two faucets (taps) probably were sold as a coded set, but the code is unusable (and ignored), as there is a single water supply.
Signaling and communication between the Astatotilapia burtoni
Chart semiotics of social networking