introductory

adj. /ˌɪn.trəˈdʌk.tɚ.i/ B2

入门的；初步的

Serving as an introduction to a subject or activity.

仙境例句

The first, introductory lesson taught the young turtles where to sit and when to be quiet.

第一堂入门课教小海龟们坐在哪里、什么时候要安静。