The words spec, speck sound the same but have different meanings and spellings. Why do spec, speck sound the same even though they are completely different words?
The answer is simple: spec, speck are homophones of the English language.
The specifications, as for a building to be constructed.
Speculation.
To write or supply specifications for.
Of or relating to specifications: a manufacturer's spec sheet.
A small spot, mark, or discoloration.
A tiny amount; a bit: not a speck of truth in her story.
To mark with specks.
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.
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").