Denshi Jisho — Online Japanese dictionary

恐 こわ frightening; terrifying
Interjection, Usually written using kana alone 
恐 かしく yours sincerely (used to sign off on letters); respectfully yours
Expression, Usually written using kana alone, Female term or language 
恐 かしこ yours sincerely (used to sign off on letters); respectfully yours
Expression, Usually written using kana alone, Female term or language 
恐恐 こわごわ fearfully; timidly; cautiously; nervously
Adverb, Adverb taking the 'to' particle 
恐恐 きょうきょう respect (epistolary usage)
Na-adjective, Interjection, Noun 
戦戦恐恐 せんせんきょうきょう trembling with fear; filled with trepidation
Na-adjective, No-adjective, Taru-adjective, Adverb taking the 'to' particle 

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