This textbook treats solids and fluids in a balanced manner,using thermodynamic restrictions on the relation between appliedforces and material responses. This unified approach can beappreciated by engineers, physicists, and applied mathematicianswith some background in engineering mechanics. It has many examplesand about 150 exercises for students to practise. The highermathematics needed for a complete understanding is provided in theearly chapters. This subject is essential for engineers involved inexperimental or numerical modelling of material behaviour.