The article discusses the problem of classification of notions (Begriffe) by Christian Wolff, particularly in his "German Logic". Wolff divides notions – as well as representations (Vorstellungen) in general – into obscure (dunkel, obscura) and clear (klar, clara). The clear notions are divided into distinct (deutlich, distincta) and indistinct (undeutlich, indistincta or confusa). And the distinct notions are divided again into complete (ausführlich, completa) and incomplete (unausführlich,

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... ompleta), and on the other hand into adequate (vollständig, adaequata) and inadequate (unvollständig, inadaequata). The aim of the paper is to analyse and to explain these types of notions and in this way to point out the crucial significance of this classification for Wolff's philosophy. The paper shows that the starting point for understanding of Wolff's theory of notions in "German Logic" is the correct interpretation of his definition of notion in this work, above all the correct interpretation of the word "Sache". It is further explained, what it means to have a notion of something by an image and to have a notion of something by bare words. And it is also analysed the difference between obscure, clear (but indistinct), distinct, complete and adequate notions.