The investigation of the cause of morphological diversity in nominative adjective in Persian

The aim of the present article is to investigate morphological diversity in nominative adjective in Persian. To reach this purpose, morphological patterns of nominativeadjective in the previous researchers’ works were gathered and criticized.To remove the weaknesses, they were presented within a new approach of “construction and interpretation”, because it was revealed the cause of morphological diversity in nominative adjective is the role of usage as the basis of conceptualization in language; In other words, by usage and interaction of it with meaning, speaker updates and creates new constructions; the listener interprets the new construction in a verbal communication and in this way, conceptualization takes place. In all patterns, nomination is central meaning but each time the speaker links some of his illocutionary force to it and creates a form with a new meaning as a different construction; so while keeping its central meaning, the new construction finds a new usage.