This ISO 14688-2 outlines the basic principles for classification of soils of those material characteristics most commonly used for soils for engineering purposes and should be read in conjunction with EN 14688-1 which gives rules for the identification and description of soils. The relevant characteristics might vary and therefore, for particular projects or materials, more detailed subdivisions of the descriptive and classification terms might be appropriate. Due to differences in local geological conditions, practices to enhance relevant classification criteria are used. The classification principles established in ISO 14688-2 allow soils to be classified into groups of similar composition and geotechnical properties, based on the results of field and laboratory tests with respect to their suitability for geotechnical engineering purposes such as: – foundations; – ground improvements; – roads; – embankments; – dams; and – drainage systems. This ISO 14688-2 is applicable to natural soil in situ, natural soil reworked artificially and synthetic materials. A more detailed classification for use in earthworks is given in EN 16907. Identification and description of rocks are covered by ISO 14689-1. Identification and description of materials intermediate between soil and rock are carried out using the procedures in ISO 14688-1, ISO 14688-2 and ISO 14689-1 as appropriate. The identification and classification of soil for pedological purposes, as well as in the framework of measurements for soil protection and for remediation of contaminated areas, is covered by ISO 11259. A text giving guidance on the classification of soils is given in Norbury (2015).