1. Introduction  
2. Data and Sample Selection  
3. Age and Metallicity Estimates from Full-Spectral Fitting  
4. The Metallicity-Mass Diagram of LEGA-C Quiescent Galaxies  
4.1. The Metallicity-Mass Diagram  
4.2. The MEME Relation  
5. The Role of Cosmic Evolution on Metallicity  
5.1. Star Formation History and Metallicity Enrichment History  
5.2. The Evolution of the Mass-Metallicity Diagram as a Function of the Formation Time  
6. Summary  
7. Discussion