Reference works include dictionaries, thesauruses, encyclopedias, almanacs, bibliographies, and catalogs (e.g. catalogs of libraries, museums or the works of individual artists).
They typically offer monolingual and bilingual dictionaries, one or more thesauruses, and technical or specialized dictionaries.
Through online dictionaries and thesauruses, users can use a word they did not know or understand before, and its definition can be checked again and again.
There are in existence alphabetical thesauruses which do not attempt to number the senses when giving synonyms but this certainly detracts from ease of use.
Precompiled thesauruses (most of them) identify equivalence and more general or specific relations.
For the thesauruses in these programs recognize far fewer forms than the spelling-checkers can, and only limited meanings for the forms they do recognize.
Unlike traditional hard-to-use thesauruses, online easy-to-use references reach the target information directly with alphabetically arranged synonyms or antonyms with both brief definitions and usage information.
