希薄・稀薄|きはくkihaku[0]heiban (flat)

1. na-adjective, nounthin (air); weak (liquid); dilute; sparse (population); rarefied
   高たかく登のぼるにつれて、空気くうきは希薄きはくになる。↗

   As you go up higher, the air becomes thinner.
2. na-adjective, nounlacking (enthusiasm, consideration, substance, etc.); insubstantial; deficient; tenuous (link)

• Related薄いうすいNeutralThe everyday word for thin or pale, used of concrete things like paper or soup; 「希薄」 is mostly for density, awareness or ties growing weak, as in 「人間関係が希薄だ」.
• Related不十分ふじゅうぶんNeutralMeans insufficient or inadequate — something falls short of what is needed. It is about quantity or quality being lacking, not about thinness or dilution.
• Related空疎くうそWrittenWritten/formal word for hollow, empty content; it criticizes arguments or writing that lack substance. 「希薄」 just says something is thin or weak, not necessarily hollow.
• RelatedまばらNeutralDescribes things scattered with gaps between them — it is about distribution, as in 「人影がまばら」. 「希薄」 is about density or degree being low.
• Related薄っぺらうすっぺらCasualColloquial and derogatory: cheaply thin or shallow, as in 「薄っぺらな人間」. 「希薄」 is a neutral word for something being thin or weak.
• Related薄弱はくじゃくWrittenWritten/formal word for weakness, as in 「意志薄弱」「根拠薄弱」; it points to a weak element, while 「希薄」 says something is faint or scarce.
• Related水臭いみずくさいCasualColloquial. For people, it means stand-offish or not frank with each other; it can also mean a drink tastes watery. 「希薄」 describes ties or awareness growing faint.
• Related水っぽいみずっぽいCasualColloquial: full of water, so the taste is diluted — said mostly of food and drink. 「希薄」 covers density, air, awareness and ties, not just flavor.
• Related足りないたりないNeutralEveryday word for not enough or lacking — an amount falls short. It says nothing about thinness or dilution, which is what 「希薄」 is about.
• Antonym濃厚のうこうNeutralAntonym: rich, strong or thick in flavor, color, smell — or a close, intense relationship. Where 「希薄」 says faint, 「濃厚」 says dense or strong.
• Antonym豊富ほうふNeutralAntonym for the 'lacking' side of 「希薄」: abundant, plentiful, ample. Use it when there is plenty of something rather than a scarce or faint amount.

Use 「希薄」 for air, awareness or human ties that are faint or scarce, as in 「人間関係が希薄だ」. In daily talk say 「薄い」 for thin or weak and 「まばら」 for sparse scattering. For hollow content use 「空疎」, for weakness 「薄弱」, for shallowness 「薄っぺら」, for not enough 「足りない」「不十分」; the opposites are 「濃厚」 and 「豊富」.

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

1. 色いろや密度みつどが小ちいさいこと。薄うすいこと。淡あわいこと。
2. 何なんらかの要素ようそが感かんじられないか、感かんじられても弱よわいこと。
3. 可能性かのうせいが低ひくいこと。