The part of the toilet seat that is commonly referred to as "it" is the seat itself, which is the flat, circular or oval surface that covers the bowl of the toilet. This part is designed to be comfortable for sitting and is typically made of materials such as plastic, porcelain, or wood.

The reason for this identification is based on the standard design and function of a toilet seat. According to a study by the American Journal of Infection Control, the toilet seat is a common surface that can harbor bacteria, making it important to identify and clean this area regularly. The seat is also the part that users come into direct contact with, which is why it is crucial to maintain its cleanliness for hygiene purposes. Data from the Centers for Disease Control and Prevention (CDC) indicates that proper cleaning and disinfection of toilet seats can significantly reduce the risk of transmitting pathogens.