A wine steward is commonly known as a sommelier. A sommelier is a trained and knowledgeable wine professional who specializes in all aspects of wine service, including wine pairing, wine selection, and wine storage. They have extensive knowledge about different types of wines, regions, and vintages, and are responsible for curating wine lists, assisting customers in choosing wines, and ensuring that wines are served and stored correctly. Therefore, the correct answer for this question is Sommelier.