虚弱|きょじゃくkyojaku[0]heiban (flat)

1. na-adjective, no-adjectivefeebleness; weakness; imbecility
   彼かれは強健きょうけんどころか実じつに虚弱きょじゃくだった。↗

   So far from being robust, he was extremely weak.

• Synonym弱いよわいNeutral「弱い」 is the everyday adjective for weak; broader than 「虚弱」, it covers strength, skill and more, not just frail health.
• Synonym脆弱ぜいじゃくWritten「脆弱」 is a written word stressing the fragility of structures or systems that easily break down, as in 「脆弱な地盤」.
• Synonym弱々しいよわよわしいNeutral「弱々しい」 describes someone or something that looks very weak; often for a feeble appearance or voice, as in 「弱々しい声」.
• Synonym病弱びょうじゃくNeutral「病弱」 stresses a weak constitution that falls ill easily; it puts more weight on sickness than 「虚弱」 does.
• Synonymか弱いかよわいCasual「か弱い」 is colloquial: it suggests a delicate frailty that invites protection, often said of women.
• Synonym柔弱にゅうじゃくWritten「柔弱」 is a rare written word: it stresses lacking strength and backbone, soft rather than robust.
• Synonym羸弱るいじゃくFormal「羸弱」 is formal and rare, with a strong literary flavor: it stresses a thin, feeble body.
• Synonymひ弱ひよわCasual「ひ弱」 is colloquial: physically or mentally not tough or resilient, as in 「ひ弱な子」.
• RelatedもろいNeutral「脆い」 is for things that break easily; it also covers being soft-hearted and quick to tears, as in 「涙もろい」.
• Related惰弱だじゃくWritten「惰弱」 is a rare written word: it suggests a listless, weak-willed lack of drive rather than mere physical weakness.
• RelatedよぼよぼCasual「よぼよぼ」 is a colloquial mimetic word for a doddering, tottering gait in old age; it does not describe inborn frailty.
• Related弱さよわさNeutral「弱さ」 is the noun form: it points to the degree of weakness or to a weak point, as in 「心の弱さ」.
• Relatedか細いかぼそいCasual「か細い」 is colloquial for something slender and weak — a body, arms or a voice — as in 「か細い声」.
• Antonym頑丈がんじょうNeutralAntonym: 「頑丈」 is solid and sturdy, for bodies and objects alike — the opposite of a frail 「虚弱」 build.
• Antonym強健きょうけんWrittenAntonym in written style: 「強健」 describes a robust, sturdy constitution — the exact opposite of 「虚弱」.

Use 「虚弱」 for physical weakness or poor constitution, as in 「虚弱体質」. Everyday weak is 「弱い」; often ill is 「病弱」; delicately frail is 「か弱い」. 「脆弱」 is for fragile structures and 「弱さ」 is the noun for weakness. The rest are rarer or narrower: 「惰弱」「柔弱」 weak-willed, 「羸弱」 formal frailty, 「ひ弱」 lacking toughness, 「脆い」 brittle or tearful, 「か細い」 thin and weak, 「よぼよぼ」 tottering with age.

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

1. 力ちからや勢いきおいが弱よわいこと。特とくに体からだが弱よわいこと。