Final answer:
In the story, a connoisseur is the term that is synonymous with an expert when referring to Fortunato's deep knowledge, and appreciation for wine.
Step-by-step explanation:
In the context of the story, Fortunato is depicted as an expert on wine. An alternative word that is synonymous with expert in this scenario is connoisseur, which implies a deep appreciation and detailed knowledge in the nuances of wine. While the other options given such as aficionado, sommelier, and enthusiast are related terms, connoisseur carries the closest association with the expertise evidenced by Fortunato in his knowledge of vintages. Sommelier, though a professional in the wine field, is typically associated with those who manage the wine service in a dining establishment, which is less indicative of the broader expertise implied by connoisseur.