The words sew, so, sow sound the same but have different meanings and spellings. Why do sew, so, sow sound the same even though they are completely different words?
The answer is simple: sew, so, sow are homophones of the English language.
To make, repair, or fasten by stitching, as with a needle and thread or a sewing machine: sew a dress; sew on a button.
To furnish with stitches for the purpose of closing, fastening, or attaching: sew an incision closed.
To work with a needle and thread or with a sewing machine.
sew up Informal To complete successfully: Our team has sewn up the championship.
In the condition or manner expressed or indicated; thus: Hold the brush so.
To the amount or degree expressed or understood; to such an extent: She was so weary that she fell.
To a great extent; to such an evident degree: But the idea is so obvious.
Because of the reason given; consequently: She was weary and so fell.
To scatter (seed) over the ground for growing.
To spread (land, for example) with seed.
To strew something around or over (an area); distribute something over.
To propagate; disseminate: sow rumors.
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.