what is the difference between ごとに and おきに?


Both ごとに and おきに appear to mean "repeatedly at intervals".

What is the difference between these two expressions?




１日おきに = ２日ごとに (every other day, every second day)  
●○●○●○●...  
  
２日おきに = ３日ごとに (every three days, every third day)  
●○○●○○●○○●...  
  
ごとに(毎に) [ごとに
@weblio](http://ejje.weblio.jp/content/%E3%81%94%E3%81%A8%E3%81%AB)  
おきに(置きに) [2日置きに
@weblio](http://ejje.weblio.jp/content/2%E6%97%A5%E7%BD%AE%E3%81%8D%E3%81%AB)

おき(置き) came from the verb 置く(leave). I think it's like "an interval (between
the actions)" here. cf. 「[間隔]{かんかく}を[置]{お}く」  




１日おきに = ２日ごとに (every other day, every second day)  
●○●○●○●...  
  
２日おきに = ３日ごとに (every three days, every third day)  
●○○●○○●○○●...  
  
ごとに(毎に) [ごとに
@weblio](http://ejje.weblio.jp/content/%E3%81%94%E3%81%A8%E3%81%AB)  
おきに(置きに) [2日置きに
@weblio](http://ejje.weblio.jp/content/2%E6%97%A5%E7%BD%AE%E3%81%8D%E3%81%AB)

おき(置き) came from the verb 置く(leave). I think it's like "an interval (between
the actions)" here. cf. 「[間隔]{かんかく}を[置]{お}く」  

