Re-training is a term that refers to the process of training someone again, usually with new skills or knowledge. The term can be replaced with synonyms such as upskilling, reskilling or re-education. Upskilling implies the process of improving the existing set of skills and knowledge to keep them updated with current trends and demands. Reskilling requires training with new skills that differ from the previous ones. It is necessary when skills become redundant or obsolete. Re-education implies formal training to learn new subjects, approaches and theories. These synonyms for re-training are interchangeable and can be used in various contexts to describe the process of learning and training.