visual cell vs rod

visual cell and rod both are nouns.

Word	Noun	Adjective	Verb	Adverb
visual cell	Yes	No	No	No
rod	Yes	No	No	No

As nouns, rod is a hyponym of visual cell; that is, rod is a word with a more specific, narrower meaning than visual cell:

Other hyponyms of visual cell include cone, cone cell, retinal cone, retinal rod, rod cell.

visual cell (noun)	rod (noun)
one of the cells of the retina that is sensitive to light	any rod-shaped bacterium
	a long thin implement made of metal or wood
	a gangster's pistol
	a visual receptor cell that is sensitive to dim light
	a linear measure of 16.5 feet
	a square rod of land