The words son, sun, sunn sound the same but have different meanings and spellings. Why do son, sun, sunn sound the same even though they are completely different words?
The answer is simple: son, sun, sunn are homophones of the English language.
One's male child.
A male descendant.
A man considered as if in a relationship of child to parent: a son of the soil.
One personified or regarded as a male descendant.
A star that is the basis of the solar system and that sustains life on Earth, being the source of heat and light. It has a mean distance from Earth of about 150 million kilometers (93 million miles) a diameter of approximately 1,390,000 kilometers (864,000 miles) and a mass about 330,000 times that of Earth.
A star that is the center of a planetary system.
The radiant energy, especially heat and visible light, emitted by the sun; sunshine.
A sunlike object, representation, or design.
A tropical Asian plant (Crotalaria juncea) having clusters of yellow flowers.
A tough fiber obtained from the stems of this plant, used for cordage.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.