How many hollow holes are behind the nose?

Behind the nose, there are two primary hollow spaces known as the nasal cavities, which are located on either side of the nasal septum. Additionally, these cavities connect to several paranasal sinuses, including the maxillary, frontal, ethmoid, and sphenoid sinuses, which also contain air-filled spaces. Thus, while there are specifically two main nasal cavities, the overall system includes multiple sinuses that contribute to the hollow structures in that area.