The words crater, krater sound the same but have different meanings and spellings. Why do crater, krater sound the same even though they are completely different words?
The answer is simple: crater, krater are homophones of the English language.
A bowl-shaped depression at the mouth of a volcano or geyser.
A bowl-shaped depression in a surface made by an explosion or the impact of a body, such as a meteoroid.
A pit; a hollow.
Variant of krater.
A wide, two-handled bowl used in ancient Greece and Rome for mixing wine and water.
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.