What's the difference between たびに, ごとに and おきに?

Question

I can't wrap my head around the difference between たびに, ごとに and おきに. I have already looked up at the answers already posted in two previous posts and on the internet, but I still don't get it.

I understand that たびに means that every time something happens the result is always the same; whereas, ごとに has basically the same meaning, but it also has the nuance of "more" as in this sentence

"君と会うごとに不満が増してゆく"

However, there are sentences as

"彼は会うたびに好きになる" and "私の孫は会うたびに、前より大きくなっている"

where たびに also bears the meaning of "more" and, thus, it can be replaced by ごとに. So what is the difference?

Moreover, I have the same problem with ごとに and おきに. They both mean "every", but they are not always interchangeable or they do not always bear the same meaning, as in

"この電車は二駅おきに止まる"

and in

"この電車は二駅ごとに止まる"

If I got it right

"この電車は二駅おきに止まる"

means that "the train stops every tree stops", while

"この電車は二駅ごとに止まる"

means that "the train stops every two stops".

On the other hand, in this sentence

"私は二日ごとに花子と会っている"

ごとに and おきに are interchangeable and bear the same meaning. Can somebody help me to figure it out?

Answer 1

おきに is different from the other two because it always implies intervals. X おきに always implies with an interval of X. You can't use it if there aren't any predictable intervals. The emphasis is on describing what happens at what interval.

This is different from たびに、ごとに because they can be used without an "interval":

見るたびに、見るごとに美しくなっていく

When used this way, the focus is on describing the correlation (when A happens, B happens). They do have slightly different nuances - ごとに implies accumulation if used where some sort of accumulation can happen. E.g.:

会うたびに重い 会うごとに重い

The above sentences have a similar meaning, but the first implies "it's emotionally taxing every time we meet", where the second implies "it's getting more emotionally taxing every time we meet".ごとに also sounds a tad archaic.

Another difference is that ごとに can be used on nouns, while たびに can't.

二日ごとに温度を測る、家ごとに水をためる　←　OK
二日たびに温度を測る、家たびに水をためる　←　NOT GOOD

Note that おきに refers to the interval (what's in between), unlike ごとに. E.g.:

二日おきに温度を測る　←　Measure every 3rd day
二日ごとに温度を測る　←　Measure every 2nd day
家おきに水をためる　←　Every second home saves water
家ごとに水をためる　←　Every home saves water

Answer 2

You say that たびに and ごとに have basically the same meaning but that isn't quite accurate. Think of たびに as 'whenever' in English - describing an event which produces the same outcome every time. In your sample sentences, the 'more' is not exactly a translation of たびに but rather an inference based on the idea of 'every (consecutive) time' something happens.

As you mentioned, ごとに and おきに are sometimes interchangeable but not always, depending on the context. The key difference is that they are more to do with intervals of time or space.

For おきに, think of two events that are separated by the stated interval. Therefore, 二駅おきに means that the two events are the train stopping once and then stopping again, with the space interval of two stations between = every third station. (Event 1 - amount of time or spaceおきに - Event 2).

For ごとに, think of it like 'every (ordinal number)'. Therefore, 二駅ごとに means every 2nd station = every other station.

Also, remember that sometimes in Japanese there is overlap in grammar structures. A concept can sometimes be expressed precisely by two or more different grammar constructions, even though those grammar structures have different usages in general. In my opinion, the important thing is to understand the primary meaning and usage of each one and not get bogged down with the exceptional cases where there might be overlap. Hope that helps.