This document contains summaries of 5 grammar lessons that teach about different types of nouns. Lesson 16 defines nouns and gives examples. Lesson 17 discusses singular and plural nouns. Lesson 18 covers proper and common nouns. Lesson 19 defines concrete, abstract, and compound nouns. Lesson 20 defines collective, count, and mass nouns. Each lesson provides examples and exercises for students to identify nouns in sentences and classify them.