Class - property - concept

It is argued that the terms class, property, concept are exactly distinguishable and that defining this distinction helps to avoiding frequently occurring misunderstandings. Classes are extensions, properties are intensions and concepts are abstract procedures, i.e., hyperintensions. Realizing these distinctions we fulfill Godel's requirement to make the meaning of the terms 'class' and 'concept' clearer and to set up a consistent theory of classes and concepts as objectively existing entities.