noun
subject index
A reference index organized by topic or subject, commonly found in books, manuals, or databases.
この本の巻末には事項索引が付いている。
This book has a subject index at the end.
索引 is a general index; 事項索引 specifically refers to an index arranged by subject or topic.
Compound of 事項 (じこう, 'matter, item') and 索引 (さくいん, 'index').