1. Not brought about by coercion or force
   - uncoerced, willing 
2. Not resulting from undue effort; not forced
   "a voice with a pleasingly unforced quality"
   - unstrained

See also: effortless, voluntary

• nightcap
• nightclothes
• nightclub
• nightcrawler
• nightdress
• nighted
• nightfall
• nightgown
• nighthawk
• nightie
• nightingale
• nightjar
• nightlife
• nightlong
• nightly
• nightmare
• nightmarish
• nightrider
• nightshade
• nightshirt
• nightspot
• nightstand
• nightstick
• nighttime
• nightwalker