How to say "unnatural" in Japanese

• 無理むりJLPT N4approx.Common
  na-adjective, nounFor 'unnatural' this covers the strained, forced kind — something pushed beyond reasonable limits — but its primary senses are 'unreasonable' and 'unjustifiable', so it is seldom the word you want here.
  それは無理むりな注文ちゅうもんだ。↗

  Your demands are unreasonable.
• 不自然ふしぜんCommon
  na-adjective, nounThe default word for most senses of 'unnatural': an unnatural smile, posture, translation, or atmosphere — anything that strikes you as not natural, affected, or strained.
  我々われわれ二人ふたりがここにいるのは不自然ふしぜんだ。↗

  The two of us don't belong here.
• 人工的じんこうてきCommon
  na-adjectiveCovers 'unnatural' in the sense of artificial: a look, flavor, or material that seems manufactured rather than natural. Choose it when the unnaturalness comes from human making, not from strain or behavior.
  人工的じんこうてきな光ひかりは電力でんりょくという手段しゅだんによって作つくられた。↗

  Artificial light is produced by means of electricity.
• 人為的じんいてきCommon
  na-adjectiveCovers 'unnatural' as human-caused: a disaster, error, or change brought about by human action rather than nature. It stresses human agency, so it suits causes and events more than appearances.

Use 不自然 for the general sense of unnatural appearance or behavior, 人工的 for an artificial, manufactured feel, 人為的 for outcomes caused by human action, and 無理 when the unnaturalness is really a matter of forcing or strain.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 無理むりunreasonable
• 不自然ふしぜんunnatural
• 人工的じんこうてきartificial
• 人為的じんいてきartificial
• わざとらしいunnatural
• 取って付けたようとってつけたようunnatural
• ざーとらしいunnatural