The correct answer is option 2: Stomach. The stomach is not considered a gland because it does not produce and secrete hormones or other substances.

Let`s review the other options:

1. Thyroid: The thyroid gland is a butterfly-shaped gland located in the neck. It produces and releases hormones that regulate metabolism and control various bodily functions.

3. Liver: The liver is the largest gland in the body. It performs many important functions, including the production of bile, which aids in digestion and the absorption of fats.

4. Pancreas: The pancreas is a glandular organ located behind the stomach. It produces digestive enzymes and hormones, such as insulin, that help regulate blood sugar levels.

In summary, while the thyroid, liver, and pancreas are all glands that produce and secrete substances, the stomach does not have glandular functions and therefore is not considered a gland.