Denshi Jisho — Online Japanese dictionary

真面 まとも 1: (Usually written using kana alone) the front;
2: honesty; uprightness; directness;
3: decency; normality
Na-adjective, Noun 
真面目 まじめ diligent; serious; honest; sober; grave; earnest; steady
Common word, Ateji (phonetic) reading, Na-adjective, Noun 
真面に まともに fair and square; flat-out; squarely
Adverb, Usually written using kana alone 
真面目さ まじめさ earnestness; solemnity; gravity; seriousness; soberness
Noun, Usually written using kana alone 
真面目 しんめんぼく 1: one's true character; one's true self; oneself;
2: seriousness; earnestness
Noun 
真面目 しんめんもく 1: one's true character; one's true self; oneself;
2: seriousness; earnestness
Noun 
真面目腐る まじめくさる to become extremely serious (in attitude); to look solemn; to assume a solemn air
Godan verb with ru ending, Intransitive verb 

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