ごとにEvery; for each
ごとに says that something happens for each successive unit, group, member, or occurrence.
The basic idea
The expression divides a sequence into units and applies the following action or fact to each unit separately. With a measured interval, it usually means one occurrence in every successive unit; with a group noun, it means handling each group separately.
Three common patterns
Notice what immediately precedes the target: a measured unit, a group, or a recurring event.
How to count the interval
A phrase such as 二日ごとに normally divides time into successive two-day units. If the first occurrence is on day one, the following occurrences are on days three, five, and seven.
Counting intervals versus leaving gaps
ごとに counts successive units, while おきに prototypically describes the gap left between occurrences. With a two-day unit, this gives the clearest contrast: the first schedule falls on days one, three, five, and seven; the second falls on days one, four, and seven. With very short units, actual usage can overlap, so established scheduling conventions matter.
一日から二日ごとに薬を飲むなら、飲む日は一日、三日、五日、七日です。
If you take the medicine every two days starting on the first, the dates are the first, third, fifth, and seventh.
Analyze一日から二日おきに薬を飲むなら、飲む日は一日、四日、七日です。
If you take the medicine with two days between doses starting on the first, the dates are the first, fourth, and seventh.
AnalyzeThis is the neighboring gap-based pattern, not the target construction.
Groups versus recurring occasions
For distributive grouping, attach the target directly to the noun: noun + ごとに. The occasion-based expression uses noun + のたびに and emphasizes every occasion on which an event happens. After a verb, the two can overlap, but only the target naturally covers measured intervals and group-by-group distribution as well.
会議のたびに同じ質問が出ます。
The same question comes up at every meeting.
AnalyzeThis example treats each meeting as a recurring occasion and therefore uses the neighboring pattern with の.
Do not confuse it with the whole-item expression
A noun followed by ごと can also mean that the whole item is included. That fixed use does not distribute an action across units and does not contain the target ending に.
りんごを皮ごと煮ます。
I simmer the apple with the skin on.
AnalyzeThis means that the skin is included; it is not an example of distributive ごとに.
More examples
このバスは十五分ごとに出ます。
This bus leaves every fifteen minutes.
Analyze三ページごとに写真があります。
There is a photograph every three pages.
Analyzeチームごとに作戦が違います。
Each team has a different strategy.
Analyze注文ごとに番号を付けてください。
Please assign a number to each order.
Analyzeこの曲は聞くごとに好きになります。
I like this song more every time I hear it.
Analyze三十メートルごとに案内板が立っています。
There is a sign every thirty meters.
Analyze