How to say "vulnerable" in Japanese

• 無防備むぼうびCommon
  na-adjective, no-adjectiveCovers the basic sense of 'vulnerable': defenseless or unprotected against danger or attack. A common word for this meaning, typical of a person or place left exposed.
• 受けやすいうけやすい
  i-adjectiveCovers 'vulnerable to' in the sense of susceptible or prone — a tendency to be affected by something, such as influence or criticism. A less common rendering; it stresses the tendency, not lack of defense.
  日本にっぽんは非常ひじょうに地震じしんの害がいを受うけやすい。↗

  Japan is very subject to earthquakes.
• 脇が甘いわきがあまい
  expression, i-adjectiveAn idiomatic expression meaning off one's guard, with weak defenses — 'vulnerable (to attack)'. It describes an unguarded person who leaves openings, and is marginal for the general sense of 'vulnerable'.

Use 無防備, the common word, for the general sense of being defenseless or unprotected, 「受けやすい」 for being susceptible or prone to something, and 「脇が甘い」 for an unguarded person vulnerable to attack.

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

• 無防備むぼうびdefenseless
• 受けやすいうけやすいsusceptible
• 脇が甘いわきがあまいhaving weak defenses