The words moat, mote sound the same but have different meanings and spellings. Why do moat, mote sound the same even though they are completely different words?
The answer is simple: moat, mote are homophones of the English language.
A deep wide ditch, usually filled with water, typically surrounding a fortified medieval town, fortress, or castle as a protection against assault.
A ditch similar to one surrounding a fortification: A moat separates the animals in the zoo from the spectators.
To surround with or as if with a moat.
A very small particle; a speck: "Dust motes hung in a slant of sunlight” ( Anne Tyler).
Archaic May; might.
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.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").