1. Method, used by computers, for developing an ontology ( 70 ) of a text ( 10 ) in natural language, comprising the steps of: receiving text data from the text ( 10 ); extracting the syntax and meaningful words ( 20 ) from the text via a grammatical analysis (S 100 ) of the received data; for each of at least some of the meaningful words ( 20 ) of the text: searching (S 200 ) for a definition ( 40 ) of that word ( 20 ) by means of at least one electronic dictionary ( 30 , 35 ), extracting the syntax and the meaningful words of that definition, and creating (S 300 ) an elementary lexical graph ( 50 ) of that definition based on the syntax and the meaningful words of that definition; and merging (S 400 ) at least two of the elementary lexical graphs ( 50 ) created, as a function of the syntax of the text, so as to create at least one semantic graph ( 60 ) of the text.