Best Science Dictionary and Dictionaries
Algorithms, Data Structures, and Problems - terms and definitions of algorithms, data structures, and classical problems in sorting, searching, combinatorics, graphs, and more.
Amateur Telescope Makers Dictionary - words in nine languages: English, French, German, Dutch, Portuguese, Spanish, Indonesian, Italian, and Russian. Definitions in English.
BioTech's Biotechnology Dictionary - free, searchable online dictionary of biology, chemistry, and biotechnology terms.
Chemistry & Environmental Dictionary - provides definitions for technical terms and acronyms, and related articles.
Dictionary of Cell and Molecular Biology - provides quick access to easily-understood and cross-referenced definitions.
Dictionary of Units, A - an explanation of the principle systems of units, their history, standards, and conversion factors for changing from one to the other.
GIS Dictionary - includes definitions for terms which either relate directly to GIS or which GIS users may come across in the course of their work.
Glossary of Botanical Terms - interactive glossary of terms relating to botany, gardening, horticulture and landscape architecture.
Glossary of Space Terms - from the NASA Jet Propulsion Laboratory.
How Many? - dictionary of units of measurement with commentaries and explanations of the English Customary, Metric, and International Systems.
Hypertext Glossary of Genetic Terms - searchable database of genetic terms with hypertext cross references and pictures.
Lexicon EncycloBio - provides biological terms, definitions with pictures, and Flash movies. Includes an internal search engine.
Mathematical Programming Glossary - glossary of terms (plus supplements) used in optimization.
Science Terms: Distinctions, Restrictions, and Confusions - discussion of familiar words that have specific or specialized meanings in science, and scientific terms that are easy to confuse. From The American Heritage Book of English Usage.
Visionary - a dictionary for the study of human and animal vision, including terms from biological and machine vision, visual psychophysics, visual neuroscience, and other related fields.
Visual Dictionary of Special Plane Curves - including description, history, formulas, properties, and links for each.
Water Words Dictionary - from the Nevada Division of Water Planning.
Web Directory: Dictionaries and Unit Conversion for Engineers