letter http://id.loc.gov/authorities/subjects/sh85076240 http://purl.bioontology.org/ontology/MESH/D016422 http://purl.obolibrary.org/obo/ENVO_02000081 http://purl.obolibrary.org/obo/NCIT_C70805 http://semanticscience.org/resource/SIO_000306 https://en.wikipedia.org/wiki/Category:Letters_(message) https://en.wikipedia.org/wiki/Letter_(message) https://www.wikidata.org/wiki/Q133492 PN4400 PN6130-PN6140 Work consisting of written or printed communication between individuals or between persons and representatives of corporate bodies. The correspondence may be personal or professional. In medical and other scientific publications the letter is usually from one or more authors to the editor of the journal or book publishing the item being commented upon or discussed. letters ephemera