Explanation:
The facial bones are the bones that make up the face. They provide support to the facial structures, protect the eyes, and form the nasal and oral cavities. The facial bones include the maxilla, mandible, zygomatic, nasal, lacrimal, palatine, and vomer bones.

Unpaired Facial Bones:
The unpaired facial bones are the bones that are located in the midline of the face and are not paired with another bone. The unpaired facial bones are:

- Vomer: The vomer is a thin, flat bone that forms part of the nasal septum, which divides the nasal cavity into two halves.
- Mandible: The mandible is the largest and strongest facial bone. It forms the lower jaw and articulates with the temporal bone to form the temporomandibular joint.
- Maxilla: The maxilla is a paired bone that forms the upper jaw and the central part of the face. It articulates with the frontal bone and the zygomatic bone.
- Ethmoid: The ethmoid is a complex bone that forms the roof of the nasal cavity and part of the orbit. It contains the cribriform plate, which allows the olfactory nerves to pass from the nasal cavity to the brain.
- Sphenoid: The sphenoid is a complex bone that forms part of the base of the skull and the floor of the middle cranial fossa. It also forms part of the orbits and the nasal cavity.

Paired Facial Bones:
The paired facial bones are the bones that are located on both sides of the midline of the face. The paired facial bones are:

- Nasal: The nasal bones are two small bones that form the bridge of the nose.
- Zygomatic: The zygomatic bones are two bones that form the cheekbones and articulate with the temporal bone, maxilla, and frontal bone.
- Lacrimal: The lacrimal bones are two small bones that form part of the orbit and contain the lacrimal gland, which produces tears.
- Palatine: The palatine bones are two bones that form the posterior part of the hard palate and part of the nasal cavity.

Therefore, the unpaired facial bone is Vomer.