The Conceptual Development of

Linguistic changes would be analyzed this article in social context and based on element of time. Development in word role is one of the linguistic changes whose root shall be sought in social construct. “Night” is one of the concepts whose fundamental semantic change in literature can be regarded as signs of great social changes in Iran. Authors attempt to seek these changes by using synchrony and diachrony analysis method. We can categorize four periods of change in word “Shab” (i.e. Night), so that Night represents nature and a epical sign in classical poems. However, with a fundamental change in social context particularly in Middle Iran, Night has become a symbolic concept of Mysticism; in historical path of Iranian nation and its changing context during Constitution and emergence of Modernism, it got an indexical status and got the meaning of mishap and fate; finally, in fourth period, it is regarded as a metaphor of political authority, so it become a figural symbol along with spreading political Tyranny in the new period.