The words seaman, semen, seamen sound the same but have different meanings and spellings. Why do seaman, semen, seamen sound the same even though they are completely different words?
The answer is simple: seaman, semen, seamen are homophones of the English language.
Plural form of seaman.
A viscous whitish secretion of the male reproductive organs, containing spermatozoa and consisting of secretions of the testes, seminal vesicles, prostate, and bulbourethral glands. Also called seminal fluid.
A viscous whitish secretion of the male reproductive organs, containing spermatozoa and consisting of secretions of the testes, seminal vesicles, prostate, and bulbourethral glands. Also called seminal fluid.
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").