The tension between precision and indeterminacy is an intrinsic feature of legal language. Specialist communication, and legal language has to be regarded as such, aims at utmost precision to avoid any form of ambiguity. On the other hand, laws and statutes define general rules for citizens and must be comprehensible to all. Moreover, they have to be adapted to changing social realities. All this leads to varying degrees of indeterminacy in the different legal systems. The paper describes indeterminacy in legal language and proposes ways to handle this problem in order to improve the management of multilingual terminology as well as to optimise the translation of legal texts. An adapted terminographical methodology based on the principles of comparative law helps to overcome the lack of equivalence between concepts from different legal systems. Another important issue is the harmonisation of the law which implies a harmonisation of legal concepts and eventually a harmonisation of terms.