In biology, antrum is a general term for a cavity or chamber, which may have specific meaning in reference to certain organs or sites in the body.
In vertebrates, it may refer specifically to:
Antrum cardiacum, a dilation that occurs in the esophagus near the stomach (forestomach)
Antrum follicularum, the cavity in the epithelium that envelops the oocyte
Mastoid antrum, a cavity between the middle ear and temporal bone in the skull
Pyloric antrum, the initial portion of the pyloric part of the stomach. This is what is usually referred to as "antrum" in stomach-related topics.
Maxillary antrum or antrum of Highmore, the maxillary sinus, a cavity in the maxilla and the largest of the paranasal sinuses
In invertebrates, it may refer specifically to:
Antrum of female lepidoptera genitalia
