Part of Textbook That Explains Word Meanings
Puzzle 19 of Animation Pack
Question is: Part of Textbook That Explains Word Meanings
and the answer is: GLOSSARY
Word Meaning:
GLOSSARY — A list of difficult words or specialized terms used in a particular book or document, or in a particular domain of knowledge, with their definitions; a list of glosses (explanatory annotations).
Definitions from Wiktionary.