This document summarizes key concepts from Roland Barthes' theory of semiotics:
1) Semiotics is the study of sign systems and how meaning is derived from signs. A signifier is the form that the sign takes and the signified is the concept it represents.
2) Signs can change in meaning over time. For example, yellow ribbons initially represented forgiveness but later represented support for American troops.
3) Signs have both a denotative (descriptive) meaning and a connotative meaning linked to cultural and ideological values. The connotative meaning is how signs can be used to reinforce dominant social and political views.