The words kill, kiln sound the same but have different meanings and spellings. Why do kill, kiln sound the same even though they are completely different words?
The answer is simple: kill, kiln are homophones of the English language.
To put to death.
To deprive of life: The Black Death was a disease that killed millions.
To put an end to; extinguish: The rain killed our plans for a picnic.
To destroy a vitally essential quality in: Too much garlic killed the taste of the meat.
Any of various ovens for hardening, burning, or drying substances such as grain, meal, or clay, especially a brick-lined oven used to bake or fire ceramics.
To process in one of these ovens.
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.