The signifier and the signified, semiology

Ferdinand de Saussure identified a sign as having two parts, the concept and the word. According to Saussure the word is the signifier and the concept is the signified. The word and concept have an arbitrary relationship. For example, the psychological concept of the tree can be various things. It can conjure up the image of a palm tree or an oak tree. However, the parts that make up the tree remain the same; leaves, bark, trunk, roots, etc. Moreover, the word tree gets its meaning from its difference from all the other words within the language. But you need context to know the meaning. The signifier plus the signified equals the sign. You need the signified in order to understand the signifier, which is the sign. Semiology gets you to think about signs and words in relation to one another. The sign is unique because it encompasses the signifier and signified.