The third stomach of a ruminant animal is also known as the omasum. Other synonyms for this term include the manyplies, psalterium, and the book stomach. The omasum plays a crucial role in the digestive process of ruminants as it helps to extract nutrients from the partially digested food that has passed through the rumen and reticulum. The term manyplies refers to the multiple folds of tissue found in the omasum, which help to increase its surface area and aid in nutrient absorption. The terms psalterium and book stomach refer to the structure of the omasum, which contains many leaves or pages that resemble those of a book or a psalter.