Rod

Rods are light-sensitive cells in the retina of the eye.

---

The rod is an Imperial unit of length, also known as the pole or perch. It is equal to 5.5 yards or 16.5 feet; 5.029 metres.

---

The rod is supposedly a species of creature that flits about in the air at such a high speed as to not be seen by the naked eye, but which can be caught on video. See: Rod (cryptozoology).