Words evolve, change and exploring those historical background allows us to "explode" a single concept into many ideas.
Making connections that may not have been apparent, unveiling the "unknown" and confronting confirmation bias.
Defining complex words allows the writer to clarify, provide accuracy and authority. Look for synonyms or subject headings and keywords.
Different disciplines apply words different ways. A psychologist will treat the term "climate change" as it relates to our mental health, while a chemist will treat the term "climate change" by analyzing the chemical changes in the environment. Each important, but very different methods of study.
An index is a list organized by subject, authors or keywords, often in alphabetic order, with a page number or other linked method to locate further information about that item.
The Columbia Granger's Index to Poetry in Anthologies by
For over a hundred years, The Columbia Granger's Index to Poetry in Anthologies has been the preeminent index for answers to questions about the world of poetry, identifying the author of a poem or the anthologies in which it can be found when only a title, first line, or last line is known. This latest edition-a "must have" for libraries-brings its index up to date as of May 31, 2006. This latest version features 85,000 classic and contemporary poems by 12,000 poets. Also included are works in translation and for the first time poetry in Spanish, Vietnamese, and French. The subject organization of the poems is especially useful. Hundreds of new subjects have been added, indexing poems on highly relevant topics such as Osama bin Laden, the war in Iraq, Dick Cheney, the Internet, and Rosa Parks, as well as timeless subjects like the Bill of Rights, unspoken love, faith, and inspiration. Our impressive team of consultants includes J. D. McClatchy, Harvey Shapiro, and former poet laureate Mark Strand. From The Norton Anthology of Poetry (2005 edition) to Poetry after 9/11 and Garrison Keillor's Good Poems, this new edition puts readers in touch with the best of the latest anthologies and the lasting favorites.
Western University Library. Aug. 26, 2016 (4:21)
TheOxford English Dictionary(OED) is widely regarded as the accepted authority on the English language. It is an unsurpassed guide to the meaning, history, and pronunciation of 600,000 words past and presentfrom across the English-speaking world.
The Cambridge Dictionary of Statistics by 
Black's Law Dictionary by
Features more than ten thousand legal terms and includes a dictionary guide and the complete United States Constitution.