Last, list all of the key terms for each concept in your topic. Keywords, subject headings, synonyms, and related terms are all words that identify and describe the concepts of your topic. In many instances, they are the same word used in different contexts.

• Keywords: generally the words used by the author of an article, book, etc. to describe its content. They are words essential to the description of the topic.
• Subject headings: controlled vocabulary - words that have been given a specifically defined meaning and then used to describe the contents of books, articles, movies, paintings, etc. They are used in online catalogs and indexes (both print and electronic).
• Synonyms: words that mean essentially the same thing.
• Related terms: words that describe a closely related concept or aspect of a concept.

When used in the right combination, these words can distinguish one specific topic from all others.