おきに

1. 1Marks a recurring time interval, as in 一日おきに, meaning every other day.Ex. 1
2. 2Marks regular spacing along a sequence, as in 20ページおきに, meaning every 20 pages.Ex. 2

Neutral in register, it is used for routines, schedules, and instructions about regular spacing. Unlike ごとに, which can mark each counted unit, おきに can indicate units left between occurrences; with larger page counts, the two can describe the same spacing.

• ごとにN3In its 'at intervals' sense, 「ごとに」 counts by cycles: 「一日ごとに」 means every day, and it takes 「二日ごとに」 to equal 「一日おきに」. 「ごとに」 can also follow nouns and dictionary-form verbs to mean 'for each unit' or 'every time one does something,' uses that 「おきに」 does not have.
• たびにN3「たびに」 follows a dictionary-form verb or noun + 「の」 (or stands alone as 「そのたびに」) and means that whenever something happens, the second event accompanies it, while 「おきに」 attaches only to quantity expressions and means repetition at a set interval. The two are not interchangeable.
• ずつN3「ずつ」 states the amount given to each recipient or done each time, as in 「二つずつ」 (two each), and after words like 「少し」 it shows gradual change. 「おきに」 describes the interval between repetitions, so the two are not interchangeable.
• 間にN4「間に」 follows verbs, adjectives, or noun + 「の」 to mark off a period within which something happens or is completed, whereas 「おきに」 attaches only to quantity expressions and means repetition at a set interval. The two are not interchangeable.
• ごろN5「ごろ」 follows time points such as 「7時」 or 「3月」 to give an approximate time ('around ...') and carries no sense of repetition, while 「おきに」 follows quantity expressions to mean something recurs at each interval. Their meanings differ, so they are not interchangeable.

一日ごとに means every day, unlike 一日おきに, but 20ページごとに and 20ページおきに can both mean every 20 pages. たびに refers to each occurrence of an event, ずつ to equal portions, 間に to a time span, and ごろ to an approximate time.