n. pl. li·brar·ies
a. A place in which reading materials, such as books, periodicals, and newspapers, and often other materials such as musical and video recordings, are kept for use or lending.
b. A collection of such materials, especially when systematically arranged.
c. A room in a private home for such a collection.
d. An institution or foundation maintaining such a collection.
2. A set of things similar to a library in appearance, function, or organization, especially:
a. A series of books issued by a publisher.
b. A collection of standard routines used in computer programs, usually stored as an executable file.
c. A collection of cloned DNA sequences whose location and identity can be established by mapping the genome of a particular organism.
d. A collection of proteins generated from the collected DNA sequences that express them, used for tracking metabolic functions of proteins in diseases such as cancer, for the synthesis of new drugs, and for other proteomics research.
[Middle English librarie, from Anglo-Norman, from Latin librārium, bookcase, from neuter of librārius, of books, from liber, libr-, inner bark of trees used as a writing material, book.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.