1. Introduction
2. What Constitutes a Domain Adaptation Problem?
3. A Brief Overview of Neural Machine Translation
4. Fine-Tuning as a Domain Adaptation Baseline, and its Difficulties
5. Data-Centric Adaptation Methods
6. Architecture-Centric Adaptation
7. Training Schemes for Adaptation
8. Inference Schemes for Adaptation
9. Case Studies for (Multi-)Domain Adaptation
10. Conclusions and Future Directions