This Technical Report defines the symbols to be used to represent physical, mechanical and thermal characteristics, as determined by methods described in relevant CEN publications, for advanced technical ceramics, including ceramic matrix composites. It is a guide for writing the symbols of quantities of these materials to avoid confusion in reporting measurements and characteristics of products.Where possible, the definitions are in accordance with the relevant parts of ISO 31 and ISO 80000. In addition the symbols used in undertaking measurements of these characteristics are also defined.