Ullage: Refers to the small air space in a wine bottle or barrel. Excessive air in the bottle increases the speed of oxidation.
Fill Level: The amount of wine in a bottle is gauged by its height in the bottle. Common descriptors are good fill, high shoulder (the wine level is even with the sloping part of the bottle just below the neck), or low shoulder. Important since fill level is an indicator of the wine’s condition and whether it has been properly stored. The air space in the bottle, called ullage, can cause harmful oxidation.