Adapted from 日本語の森's N3 compilation video, 0:00:00-0:08:11

Each of these phrases are used with nouns, verbs, and counters to indicate something happens every time or whenever something else occurs.

For each of these examples below, an English translation is provided in a hidden box.

1. あの先生は授業(じゅぎょう)ごとに宿題(しゅくだい)がでる。
   • answer That teacher gives out homework every time there's class.
2. あの先生は授業(じゅぎょう)のたびに宿題(しゅくだい)がでる。
   • answer That teacher gives out homework every time there's class.

1. 会うごとに好きになっていくよ。
   • answer Every time we meet I fall in love.
2. 見るたびに可愛くなっていくよね。
   • answer They are cute every time I see them.

1. この本は１ページごとにおもしろくなる。
   • answer Each page of this book is interesting.
   • Note that ページ is not a time or distance, so おきに cannot be used.
2. 電車が１０分ごとにくる。
   • answer The train comes every 10 minutes.
3. 電車が１０分おきにくる。
   • answer The train comes every 10 minutes.

One exception to note for 数量詞 is that ごとに and おきに have different meanings in the case of talking about 1 of something.

• １年ごとに = one time in one year
• １年おきに = one time in two years

Presumably this is because おきに implies that the instance lasted for a year? I'm not sure.