Semantic guarantee is considered to be the principle applied to the construction, development and evaluation of Knowledge Organisation Systems (KOS) to justify and validate meanings. In this book, we have tried to establish some arguments and inputs for a theoretical reflection relevant to the structuring components of knowledge organisation, specifically the principle of semantic guarantee, problematising aspects of meaning and sensitising elements that favour multiple points of view and possibilities of analysis in the face of the field's study issues. It can be seen that semantic guarantee is best understood in the argument in favour of the existence of facts and phenomena in reality that are capable of meaning, covering a series of aspects and precepts related to the configuration of meaning in SOCs, capable of guiding them in their projection, development and evaluation. From this reflective excursion into the frontiers of the domains of language and knowledge, the author hopes that the field of knowledge organisation will acquire more conditions and theoretical tools to deal with new (and old) issues in the processes of knowledge organisation and representation.