The ethmoid sinus is a group of small air-filled spaces located within the ethmoid bone, which is situated between the eyes and forms part of the nasal cavity. These sinuses play a role in reducing the weight of the skull, humidifying inhaled air, and enhancing voice resonance. They are divided into anterior and posterior groups, each draining into the nasal cavity. Inflammation or infection of the ethmoid sinus can lead to a condition known as sinusitis, causing symptoms such as nasal congestion, facial pain, and headaches. Treatment often involves decongestants, nasal sprays, or, in severe cases, antibiotics to alleviate the symptoms and restore normal function.