The words thyme, time sound the same but have different meanings and spellings. Why do thyme, time sound the same even though they are completely different words?
The answer is simple: thyme, time are homophones of the English language.
Any of several aromatic Eurasian herbs or low shrubs of the genus Thymus, especially T. vulgaris, of southern Europe, having small, white to lilac flowers grouped in headlike clusters.
The leaves of this plant used as a seasoning.
A nonspatial continuum in which events occur in apparently irreversible succession from the past through the present to the future.
An interval separating two points on this continuum; a duration: a long time since the last war; passed the time reading.
A number, as of years, days, or minutes, representing such an interval: ran the course in a time just under four minutes.
A similar number representing a specific point on this continuum, reckoned in hours and minutes: checked her watch and recorded the time, 6:17 A.M.
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").