Introduction Fundamental Concepts The Cluster Expansion The Cluster Operator Other Cluster-Based Wavefunctions Size-Extensivity and Size-Consistency Formal Coupled-Cluster Theory Construction of the General CC Equations Truncation of the CC Equations A Variational Coupled-Cluster Theory? The Hausdorff Expansion Practical Coupled-Cluster Theory Normal-Ordered Operators Wick's Theorem The Normal-Ordered Hamiltonian Algebraic Construction of the CCD Equations Diagrammatic Construction of the CCD Equations Second Quantization Creation and Annihilation Operators Second-Quantized Representation of Operators Usefulness of Second-Quantized Operators Relationship to Configuration Interaction References Index