The invention relates to a method of querying technical domains that recognizes the concepts represented by strings of characters, rather than merely comparing strings. It can be used to compute conceptual similarity between terms, The method employs string distance metrics and a cyclic progression of lexical processing to recognize constituent term concepts that are then combined to form full-term concepts by means of a grammar. Terms can be extracted and identified as being conceptually similar (or dissimilar) to other terms even if they have never previously been encountered. A key advantage is the ability to extract terms from documents based on the combination of a limited number of sub-concepts, This avoids the need for the prior identification of all possible terms that current methods require. A second key advantage is the ability to introduce or remove concepts and synonyms individually without the need to alter terms which the concept or synonym constitutes.