The words leased, least sound the same but have different meanings and spellings. Why do leased, least sound the same even though they are completely different words?
The answer is simple: leased, least are homophones of the English language.
Simple past tense and past participle of lease.
Transferred under the terms of a lease.
Lowest in importance or rank.
Smallest in magnitude or degree.
Slightest or tiniest: didn't care the least bit.
To or in the lowest or smallest degree.
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.