 Principles of Teaching – Structure of a Lesson In this video, we will learn about the structure of a lesson, including how many parts there are in a lesson, the function of each part, and the proportion of time used for each part. Let's go! Every lesson has three parts. The functions of the three parts of a lesson are, the first part is the introduction, the second is the new information, and the third part is a review. The proportions of time used for each part are, the introduction is one-fifth of the total lesson time, the new information is three-fifths, and the review is the last one-fifth. Let's review the key ideas to remember. Every lesson has three parts. First is the introduction, it takes one-fifth of the lesson's time, second is the new information, it takes three-fifths of the time, and third is a review. It takes the final one-fifth of the lesson time.