Denshi Jisho — Online Japanese dictionary

1: pain; anguish; suffering; distress; anxiety; worry; trouble; difficulty; hardship;
2: (Buddhist term) duhkha (suffering)
Noun 
くど this painful world; magnesia
Noun 
くみ bitterness; bitter taste
Noun, No-adjective 
くみ bitterness; bitter taste
Noun, No-adjective 
こそ kousso (African flowering plant, Hagenia abyssinica); kosso; cusso; koso; brayera
Noun, Usually written using kana alone 
くげん candid (frank) advice; exhortation
Common word, Noun, No-adjective 
くしん pain; trouble; anxiety; diligence; hard work
Common word, Noun, Suru verb 
くせん hard fight; close game
Common word, Noun, Suru verb 
くつう pain; agony; bitterness
Common word, Na-adjective, Noun, No-adjective 
くなん suffering; distress; hardship; trial
Common word, Noun 
くのう suffering; distress; affliction; anguish; agony; trouble
Common word, Noun, Suru verb 
くりょ rack one's brains
Common word, Noun, Suru verb 
くろう troubles; hardships
Common word, Na-adjective, Noun, Suru verb 
にがい bitter
Common word, Adjective 
にがて 1: poor (at); weak (in); not very good (at);
2: dislike (of)
Common word, Na-adjective, Noun 
にがみ bitterness; bitter taste
Common word, Noun, No-adjective 
くえき hard toil
Noun, No-adjective 
くかん coldest time of the year; bitter suffering
Noun 
くがい 1: (Buddhist term) world of suffering;
2: life of prostitution
Noun 
くがく paying one's own school expenses by working
Noun, Suru verb 
くぎん laborious composition; struggling to compose a poem
Noun, Suru verb 
くせつ unswerving determination
Noun 
くたい truth of suffering
Noun, Buddhist term 
くちく Japanese timber bamboo (Phyllostachys bambsoides); giant timber bamboo; madake
Noun 
くっそ kousso (African flowering plant, Hagenia abyssinica); kosso; cusso; koso; brayera
Noun, Usually written using kana alone 
くとう agonizing
Noun, Suru verb 
くない 1: mediaeval tool for digging, prying, etc.;
2: (Colloquialism) Ninja throwing knives
Noun 
くにく desperation measure
Noun 

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