1. introductory

adjective. (ˌɪntrəˈdʌktɝi, ˌɪntroʊˈdʌktɝi) Serving to open or begin.

3. introductory

adjective. (ˌɪntrəˈdʌktɝi, ˌɪntroʊˈdʌktɝi) Serving as a base or starting point.