Merriam-Webster Collegiate Dictionary - twelve

 noun  Etymology: Middle English, from Old English twelf; akin to Old High German zwelif ~, Old English twa two, -leofan (as in endleofan eleven) — more at two, eleven  Date: before 12th century  1. — see number table  2. capitalized  a. the ~ original disciples of Jesus  b. the books of the Minor Prophets in the Jewish Scriptures  3. the 12th in a set or series  4. something having 12 units or members  5. plural ~mo  • twelfth adjective or noun  • ~ adjective  • ~ pronoun, plural in construction