Dynamics of structure in relationships among words via communication is studied by a constructive approach. Our study is based on the dynamical view of language, which is that meanings of words are dynamically created through activities of sense-making by individual language users. We simulate “conversation” in which agents having word relation matrices as their internal structure speak and listen to sentences. The sense-making activity is modeled by situating words in a web of relationships among words according to the usage of the words. We observe that agents develop cluster structure in word relationships, which is endowed with both stability and adaptability. It is considered that the cluster structure shares some features with prototype category. The structure changes dynamically by appearing new usages of language. The coexisting commonality and individuality of cluster structure is observed in an ensemble of individuals.