This book examines the notions of dimension and decomposition for module categories. It discusses some basic properties of quasidecomposition functions and the complete lattice of all quasidecomposition functions taking values in a fixed given lattice.

1. Quasidecomposition functions 2. Assassin functions 3. Radical functions 4. Associated ideal functions 5. The function 6. Coirreducible modules 7. Decompositions 8. Quasidimension functions 9. The function 10. Relations between quasidecomposition functions and quasidimension functions 11. Linearization of quasidecomposition and quasidimension functions 12. Gabriel dimension 13. Torsion-theoretic Krull dimension 14. GRK-dimension 15. Classical Krull dimension