What is a dictionary?
A dictionary is a resource which lists the words in a language alphabetically, along with their definitions, usages, etymology, pronunciations, and, sometimes, translations. Dictionaries are concerned with linguistic information.
There are several types of dictionaries -- monolingual, bilingual, etymological. In addition, there are dictionaries which resemble encyclopedias in that they are collections of words related to a specific subject.
A monolingual dictionary lists the words of a single language with their definitions.
A bilingual dictionary connects the words of one language to the words of another language.
An etymological dictionary provides the etymology of words. The etymology of a word is its origin and the development of its meaning and usage over time. The meaning of words is not static, and, in research, it is critical to understand and to analyze words in the context of their usage.
A specialized or technical dictionary is a dictionary which focuses on a specific subject.
A glossary is an alphabetical list of vocabulary with definitions in a particular area of knowledge. It is a resource which can stand alone, but is most often found attached to another resource.