Which ingredient is unique to the Greek Omelet compared to other omelets?

The Greek Omelet is distinctive primarily because of the inclusion of black olives. This ingredient is emblematic of Greek cuisine, which features olives as a staple due to their historical significance and culinary versatility. The use of black olives in the Greek Omelet not only adds a characteristic flavor profile but also reflects the Mediterranean dietary traditions that emphasize fresh vegetables, herbs, and healthy fats.

Other options, such as ham, steak, and cheddar, are commonly found in various types of omelets across different culinary styles but do not specifically define the Greek version. The presence of black olives sets the Greek Omelet apart, making it unique and representative of Greek flavors and ingredients.