Abstract We present a study regarding basic level of concepts in conceptual categorization. The basic level of concepts is an important phenomenon studied in the psychology of concepts. We propose to utilize this phenomenon in formal concept analysis to select important formal concepts. Such selection is critical because, as is well known, the number of all concepts extracted from data is usually large. We review and formalize the main existing psychological approaches to basic level which are presented only informally and are not related to any particular formal model of concepts in the psychological literature. We argue and demonstrate by examples that basic level concepts may be regarded as interesting, informative formal concepts from a user viewpoint. Interestingly, our formalization and experiments reveal previously unknown relationships between the existing approaches to basic level. Thus, we argue that a formalization of basic level in the framework of formal concept analysis is beneficial for the psychological investigations themselves because it helps put them on a solid, formal ground.