The dividing line between specialised lexicography and terminography is non-existent. The focus of preparing dictionaries for a particular subject-field should be the needs of its user group in specific situations. This is catered for by the modern theory of dictionary functions and includes the introduction of subject-field components in dictionaries. Dictionary functions are communication-orientated or cognition-orientated, and the lexicographers must identify the relevant functions and select and present the data so that the dictionary satisfies the needs of the users. The optimal dictionary contains aided fully integrated subject-field components that supplement and complement the data included in the articles.