NLM collects subject-relevant dictionaries and glossaries of terms, names, subjects, phrases, abbreviations, acronyms and symbols in all languages.

Bilingual and polyglot reference tools are collected more selectively, with emphasis on those containing English terminology or otherwise of value to U.S. researchers (for example, a dictionary that contains medical terminology from a less widely read language to a more commonly read language).

NLM collects encyclopedias that support biomedical and health research and scholarship. The collection emphasizes English language works, but other languages are selected if they are of scholarly importance.

NLM very selectively collects examples of medical dictionaries and encyclopedias written for U.S. consumers to document the dissemination of public health information. Collecting emphasis is on works edited by leading experts or endorsed by major professional organizations.