This book constitutes the proceedings of the 26th International Conference on Conceptual Structures, ICCS 2021, held virtually in September 2021.The 12 full papers and 4 short papers presented were carefully reviewed and selected from 25 submissions. theory on conceptual structures, and mining conceptual structures.

Applications of Conceptual Structures.- On the use of FCA models in static analysis tools to detect common errors in programming.- Nested conceptual graphs for information fusion traceability.- Generating Layered Enterprise Architectures with Conceptual Structures.- An Approach to Identifying the Most Predictive and Discriminant Features in Supervised Classification Problems.- Combining Implications and Conceptual Analysis to Learn from a Pesticidal Plant Knowledge Base.- Ranking Schemas by Focus: A Cognitively-Inspired Approach.- Theory on Conceptual Structures.- Improving the Performance of Lindig-style Algorithms with Empty Intersections.- Quantifying the Conceptual Error in Dimensionality Reduction.- Conceptual Relevance Index for Identifying Actionable Formal Concepts.- Attribute Selection using Contranominal Scales.- Packing Problems, Dimensions and the Tensor Product of Complete Lattices.- Mining Conceptual Structures.- Random generation of a locally consistent spatio-temporal graph.- Mining Contextual Rules to Predict Asbestos in Buildings.- Temporal sequence mining using FCA and GALACTIC.- Restricted Bi-pattern Mining.- A Semantic-Based Approach for Assessing the Impact of Cyber-Physical Attacks: a Healthcare Infrastructure Use Case.