The words terce, terse sound the same but have different meanings and spellings. Why do terce, terse sound the same even though they are completely different words?
The answer is simple: terce, terse are homophones of the English language.
Variant of tierce.
Brief and to the point; effectively concise: a terse one-word answer.
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").