Preface of the special issue dedicated to selected semigroup papers from the Conference on Theoretical and Computational Algebra 2023.

The Conference on Theoretical and Computational Algebra 2023 (TCA 2023) took place in Pocinho, Portugal, attracting over 80 researchers from Europe, Australia, Brazil, Canada, and the USA. The conference covered various topics in algebra and automated reasoning, with a significant focus on semigroup theory. As a result, the editors of 'Semigroup Forum' decided to dedicate a special issue to selected papers from TCA 2023. This issue includes 11 papers that underwent a rigorous refereeing process, with additional papers still under review for future publication. The conference also honored Dr. Gracinda M. S. Gomes, a retired professor from the University of Lisbon, who made significant contributions to semigroup theory and fostered collaboration between Portugal and the UK. [Extracted from the article]