means A man who has taken religious vows and lives apart from ordinary society, usually in a community devoted to prayer, discipline, and worship.

from From Greek 'monos,' meaning 'alone' or 'single' — the same root behind 'monopoly' and 'monologue.' It became Late Latin 'monachus,' the solitary one, and traveled into Old English as 'munuc.' The irony is built into the word: monks are called 'the alone' even when they live packed together in monasteries — because the name first described hermits who genuinely withdrew to the desert by themselves, before the communal life took over.