PurposeThis paper informs about the publication of the second edition of the Integrative Levels Classification (ILC2), a freely-faceted knowledge organization system (KOS), and reviews the main changes that have been introduced as compared to its first edition (ILC1).Design/methodology/approachThe most relevant changes are illustrated, with special reference to those of interest to general classification theory, by means of examples of notation for individual classes and combinations of them.FindingsChanges introduced in ILC2 include: the names and order of some main classes; the development of subclasses for various phenomena, especially quantities and algebraic structures; the order of facet categories and the new category of Disorder; notation for special facets; distinction of the semantical function of facets (attributes) from their syntactic function. The system can be freely accessed online through a PHP browser as well as in SKOS format.Research limitationsOnly a selection of changed classes is discussed for space reasons.Practical implicationsILC1 has been previously applied to the BARTOC directory of KOSs. Update of BARTOC data to ILC2 and application of ILC2 to further information systems are envisaged. Possible methods for reclassifying BARTOC with ILC2 are discussed.OriginalityILC is a newly developed classification system, based on phenomena instead of traditional disciplines and featuring various innovative devices. This paper is an original account of its most recent evolution.