Binding affinity refers to the strength of interaction between two molecules that form a complex, such as a protein and a ligand. Synonyms for binding affinity include affinity, avidity, strength of binding, thermodynamics of binding, and binding strength. These terms describe the same concept of how strongly two molecules bind together and can be used interchangeably. The measurement of binding affinity is crucial in drug discovery and development, as molecules with high binding affinities are more potent and effective in treating diseases. Various assays and techniques, such as surface plasmon resonance and isothermal titration calorimetry, are used to measure binding affinity.