what is the difference between ごとに and おきに?

Question

Both ごとに and おきに appear to mean "repeatedly at intervals". What is the difference between these two expressions?

Answer 1

Thank you for a good question! You are right, a lot of times they are pretty much interchangeable, like:

１時間 おきに・ごとに　トイレに行（い）ったので　全然（ぜんぜん）　寝（ね）れなかった！

-I couldn't sleep at all because I had to go to the bathroom every hour!

花（はな）の　水遣り（みずやり）は　一日（いちにち）おき・ごとで　いいです。

-You may water flowers every other day.

However it is useful to know a few things about these two words:

1. おき・おきに always follows the number or quantity to express that there is an interval of that number
2. ごと・ごとに　comes after a noun or an attributive verb to say: every time of

夜毎（よごと）来年（らいねん）の東京（とうきょう）オリンピックのことを考（かんが）える。

Every night, I dream of Tokyo Olympic Games in 2020.

In this sentence, you cannot use おきに, because it is not a number but a noun 夜（よる）is placed in front.

Hope this explains!