コウ 
き.く ききめ なら.う 
() merit () efficacy () efficiency
        
ききめ (n) effect, virtue, efficacy, impression
きく (v5k,vi) (1) to be effective, to show effect, (2) to do its work, to carry out its function well, (3) to be possible to use
こうか (n,adj-no) effect, effectiveness, efficacy, result
こうかてき (adj-na) effective, successful
こうのう (n) effect, efficacy, virtue, benefit
こうよう (n) use, utility, effect, benefit
こうりつ (n) efficiency, efficacy, performance, utility factor
こうりつてき (adj-na) efficient
こうりょく (n) effect, efficacy, validity, potency

Links: KanjiDic: EDict : Wikimedia
Etymologies: 中文字譜 : 説文解字