The words sleight, slight sound the same but have different meanings and spellings. Why do sleight, slight sound the same even though they are completely different words?
The answer is simple: sleight, slight are homophones of the English language.
Deftness; dexterity.
A clever or skillful trick or deception; an artifice or stratagem.
Small in size, degree, or amount: a slight tilt; a slight surplus.
Lacking strength, substance, or solidity; frail: a slight foundation; slight evidence.
Of small importance or consideration; trifling: slight matters.
Small and slender in build or construction; delicate.
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").