The words resistance, resistants sound the same but have different meanings and spellings. Why do resistance, resistants sound the same even though they are completely different words?
The answer is simple: resistance, resistants are homophones of the English language.
The act or an instance of resisting or the capacity to resist.
A force that tends to oppose or retard motion.
An underground organization engaged in a struggle for national liberation in a country under military or totalitarian occupation.
Psychology A process in which the ego opposes the conscious recall of anxiety-producing experiences.
Plural form of resistant.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition, from Wiktionary, Creative Commons Attribution/Share-Alike License and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.