periodicity
周期
https://source.unsplash.com/featured/?periodicity#.png
/suto3/google.iconperiodicity
/suto3/Google画像検索.iconperiodicity
/suto3/Google定義検索.icon periodicity
/suto3/wikipedia.iconperiodicity
/suto3/weblio.icon periodicity
/suto3/kotobank.icon periodicity
/suto3/jisho.icon periodicity