The words turban, turbine sound the same but have different meanings and spellings. Why do turban, turbine sound the same even though they are completely different words?
The answer is simple: turban, turbine are homophones of the English language.
A traditionally Muslim headdress consisting of a long scarf of linen, cotton, or silk that is wound around a small cap or directly around the head.
A woman's close-fitting hat that consists of material wound around a small inner cap.
Any of various machines in which the kinetic energy of a moving fluid is converted to mechanical power by the impulse or reaction of the fluid with a series of buckets, paddles, or blades arrayed about the circumference of a wheel or cylinder.
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.