How to say "undesirable" in Japanese

• 悪いわるいJLPT N5approx.Common
  i-adjectiveTakes 'undesirable' in the plain sense of bad: something judged not good in itself, such as poor quality or an unwelcome result. It states a negative evaluation rather than a feeling of dislike.
  「顔色かおいろがわるいけど具合ぐあいが悪わるいのかい」「そういうわけでもないよ」↗

  "You look pale. Are you sick?" "Not exactly."
• いやJLPT N5approx.Common
  na-adjectiveCovers 'undesirable' as felt by the speaker: unpleasant, disagreeable, even nasty or horrible, something you would rather avoid or not experience. Use it when dislike or aversion, not badness, is the point.
  この卵たまごは嫌いやな匂においがする。↗

  This egg has a bad smell.

Use 「悪い」 for the plain 'bad' sense of undesirable — something judged not good or unwelcome in itself — and 「いや」 when the stress falls on subjective unpleasantness, something disagreeable or nasty that you personally dislike.

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

• 悪いわるいbad
• 芳しくないかんばしくないpoor
• 好ましからざるこのましからざるunwelcome
• いやunpleasant