The words farming, pharming sound the same but have different meanings and spellings. Why do farming, pharming sound the same even though they are completely different words?
The answer is simple: farming, pharming are homophones of the English language.
The business of cultivating land, raising stocks etc.
Pertaining to the agricultural business.
Raising livestock or fish.
Present participle of farm.
The production of pharmaceuticals from genetically altered plants or animals.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License, 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").