At the beginning of the 20th century, lexicography aimed to investigate practical and theoretical problems in the development of dictionaries. This book is no exception to this concept, as we analyse the microstructure of monolingual dictionaries distributed by the PNLD (National Textbook Programme), showing whether their aspect is favourable to the cognitive process of primary and secondary school students in public schools where these dictionaries are distributed. The microstructure analysed was based on the lexical field 'bathroom', in order to make a solid investigation possible, without losing sight of its main motivation, which is driven by the deficiency that students have in seeing the dictionary as a complex linguistic product, having a conception that a dictionary is only the result of applying a method to the verbal cohesions called words.