from The American Heritage® Dictionary of the English Language, 4th Edition
- Half: demirelief.
- To some degree; part; partly: demigod.
from Wiktionary, Creative Commons Attribution/Share-Alike License
from the GNU version of the Collaborative International Dictionary of English
- A prefix, signifying half.
Middle English demi, a half of a measure or unit, from Old French, from Medieval Latin dīmedius, from Latin dīmidius, divided in half : dis-, dis- + medius, half; see medium.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin dimidium divided in half, via Old French and Middle English demi- half (Wiktionary)