Dictionaries are essential tools for finding translations and synonyms.
The electronic dictionaries Termium Plus and Grand dictionnaire terminologique (now part of Vitrine linguistique) provide translations and definitions for technical terms in English and French.
Encyclopedias provide summary information about a certain field or topic. They are an excellent starting point for someone who is not familar with a certain subject.
Techniques de l'ingénieur is a French language encyclopedia that is an excellent source of information for all fields of engineering.