# The role of "once" in "once every X days"

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#### meijin

##### Senior Member
Hi, I'm wondering if the addition of "once" makes the phrase "every X days" mean any different. I mean, why do you add it when you add it?

For example, if you see your doctor
"once every three days", does it mean any different from seeing your doctor just "every three days"?
Can "once every three days" mean pattern 2 below? (I'm 100% sure "every three days" means pattern 1.)

• #### lingobingo

##### Senior Member
Your interpretation is right. Unless otherwise specified, it simply means at 3-day intervals. There would normally be no need to add “once” – unless there was some reason to make it clear that twice or more was not meant (for example, in dosage instructions for a medication).

#### meijin

##### Senior Member
Thanks lingobingo. Am I right in thinking that "once every three days" is the only natural way to describe pattern 2?

#### lingobingo

##### Senior Member
If you say either every 3 days or once every 3 days, the natural assumption will be a regular pattern, even if that’s not stated. If an irregular pattern is meant, no one will know that unless you spell it out.

#### meijin

##### Senior Member
If you say either every 3 days or once every 3 days, the natural assumption will be a regular pattern, even if that’s not stated.
If I said "I go to see the doctor every three days" and later showed you my calendar showing patter 2 above, would you say, "That's NOT every three days"? If so, is it better to say "once every three days"?

If an irregular pattern is meant, no one will know that unless you spell it out.
How would you spell that out in English if you didn't have the calendar with you? Would you write down the numbers? Or would you explain like "I go to the doctor on one of the first three days, then go there again on one of the following three days, then..."?

#### JulianStuart

##### Senior Member
Thanks lingobingo. Am I right in thinking that "once every three days" is the only natural way to describe pattern 2?
Pattern 2 is not described by "once every three days" or "every three days". It could be described as "five times in 15 days in an irregular fashion" or similar. As Lingo says, "every interval" implies a regularly spaced pattern. In fact, pattern 2 isn't really even a pattern If pattern 2 happens every 15 days ( ) then you would have to spell it out: "I go on days 1,5, 7, 12 and 13 in each 15 day cycle" - there's no shorter way to specify it

#### lingobingo

##### Senior Member
If I said "I go to see the doctor every three days" and later showed you my calendar showing patter 2 above, would you say, "That's NOT every three days"? If so, is it better to say "once every three days"?
It’s every 3 days whether what’s meant is the same time every day or a different time every day. They are two separate things. Adding once makes no difference apart from making it clear that it’s no more than once a day.
How would you spell that out in English if you didn't have the calendar with you? Would you write down the numbers? Or would you explain like "I go to the doctor on one of the first three days, then go there again on one of the following three days, then..."?
If you needed to explain an irregular pattern, you would do so in whatever way was most appropriate to the situation.

cross-posted

#### meijin

##### Senior Member
In fact, pattern 2 isn't really even a pattern If pattern 2 happens every 15 days ( ) then you would have to spell it out: "I go on days 1,5, 7, 12 and 13 in each 15 day cycle" - there's no shorter way to specify it
If you needed to explain an irregular pattern, you would do so in whatever way was most appropriate to the situation.
Thanks both. Maybe Julian knows this, but in Japanese there's a very commonly used short expression that describes pattern 2, and we consider it a pattern (although many of us don't wonder what that short expression really means). So you know why I've been so particular about the difference between the two expressions above.

#### lingobingo

##### Senior Member
On one occasion when I had to call out an ambulance for my little old mum, her heartbeat was not quite as it should have been. But the paramedic said don’t worry, it’s regularly irregular! I guess that’s the case here too.

#### JulianStuart

##### Senior Member
Thanks both. Maybe Julian knows this, but in Japanese there's a very commonly used short expression that describes pattern 2, and we consider it a pattern (although many of us don't wonder what that short expression really means). So you know why I've been so particular about the difference between the two expressions above.
The irregular one would normally only be called a "pattern" when it is "repeated (once) every X days" - this uses the definition of pattern referring to the distinction bewteen a pattern of events and a set of randomly spaced events.

#### meijin

##### Senior Member
The irregular one would normally only be called a "pattern" when it is "repeated (once) every X days"
Yes, but both patterns 1 and 2 above are repeated "(once) every three days", aren't they? So pattern 2 is also a pattern, isn't it?

#### JulianStuart

##### Senior Member
Yes, but both patterns 1 and 2 above are repeated "(once) every three days", aren't they? So pattern 2 is also a pattern, isn't it?

Pattern 2 cannot be repeated every three days because the sequence is 15 days long. There are two intervals (one of 3 days and one of 4 days) where nothing happens. It is "on average" that there are 5 events in 15 days (and 15/5 = 3) but that is NOT the meaning of "once every three days". "Pattern 2" cannot be described that way.

#### meijin

##### Senior Member
I'm sure you consider "once a week" a pattern (or maybe I misunderstand the meaning of the word 'pattern'? ), so I suppose one needs to describe pattern 2 as "once a/every three-day period" to make it a pattern although it is unidiomatic?

#### JulianStuart

##### Senior Member
I'm sure you consider "once a week" a pattern (or maybe I misunderstand the meaning of the word 'pattern'? ), so I suppose one needs to describe pattern 2 as "once a/every three-day period" to make it a pattern although it is unidiomatic?
Yes, once a week is a pattern. The events in what you call pattern 2 are not regular so you cannot, cannot, cannot say "every three days" or "every three day period" - if you insist on using "three days" in your expression you MUST use the term "on average". The irregular sequence in "pattern 2" only becomes a pattern if it is itself repeated every 15 or more days.

You were correct in the OP "I'm 100% sure "every three days" means pattern 1.)"

#### meijin

##### Senior Member
Yes, once a week is a pattern. The events in what you call pattern 2 are not regular so you cannot, cannot, cannot say "every three days" or "every three day period"
By any chance, does the "once" in "once a week" have to happen on the same day of the week in English? (But that would be "weekly" in my opinion.) In Japanese, it's not. If I go to a gym on Wednesday this week, Monday next week, Friday the week after next, and so forth, it's still "once a week" in Japanese. It's the same as pattern 2 above. The only difference is whether it's a seven-day period or three-day period. Maybe I'm missing something very important? I'm sorry, I still don't understand.

#### JulianStuart

##### Senior Member
Every three days means: day 1 day 4 day 7 etc (i.e.wherere each interval is, well three days!). Day1, day 2 and day 7 is NOT every three days. "Once a week" does not require it to be the same day each week (although it often is), while (once) every seven days does require the gaps be 7 days. If it is always the same day, and that is important to the communication, one could either say every seven days or e.g., every Tuesday.

You were correct in the OP "I'm 100% sure "every three days" means pattern 1.)"
Just to re-re-iterate, that's all it ever means.

Perhaps there's an expression in Japanese that means what you want but, one more time, in Engish you must add "on average" if the interval between events is a variable.

#### meijin

##### Senior Member
Every three days means: day 1 day 4 day 7 etc (i.e.wherere each interval is, well three days!). Day1, day 2 and day 7 is NOT every three days.
Well, I don't blame you, Julian, but you've clearly misunderstood my replies (or I've misunderstood your replies ). I have ABSOLUTELY no problem with "every three days". And I learned from lingobingo's replies that "once every three days" does NOT mean what I thought it might mean. What I am wondering is just this. Aren't "once every 7-day-long period (=once every week, if the 7-day-long period begins from Sunday or Monday)" and "once every 3-day-long period" both a pattern? If you call only the former a pattern, is that because there's no word like "week" for the latter?

#### JulianStuart

##### Senior Member
The "pattern" definition I tried to explain in #10 is where the following numbers form a pattern (or are formed not at random). If you ask people "Do you see the pattern in the number series below?" they will say yes.
1 1 2 3 5 8 13 21 ...(Fibonacci)
2 4 6 8 10 12 ...
2 4 8 16 32 64 ...
3 9 27 81 ...
If you ask them about the series in your "pattern 2" they will be puzzled and probably say "No, they're some sort of random progression - there's no pattern to the series."
1, 5, 7, 12 and 13

to describe pattern 2 as "once a/every three-day period" to make it a pattern although it is unidiomatic?
and that was what I responded to - you cannot do that to describe "pattern 2"

#### meijin

##### Senior Member
Well, then why did you call once a week a pattern when the intervals between the days are random?

#### JulianStuart

##### Senior Member
Once a week is a pattern (this definition meaning regular in some way), once every three days is a pattern,

Every three days: Day 1, day 4, day 7 (pattern = each number is three greater than the previous)
Every week/7 days: day 1, day 8, day 15 (pattern = each number is seven greater than the previous)
1 1 2 3 5 8 13 21 ...(Fibonacci) (pattern =each number is the sum of the previous two)
2 4 6 8 10 12 ...(pattern = each number is two greater than the previous)
2 4 8 16 32 64 ... (pattern = each number is two times the previous number)
3 9 27 81 ... (pattern = each number is three times the previous number)
are all "patterns"

Your schedule/scheme 2= 1, 5, 7, 12 and 13 (pattern is ???

With another definition of pattern, any arrangement of anything can form a pattern - this meaning does not sarry the repetition/regularity meaning. Pattern 2 could come under such a definition but it cannot be described as (regularly) every three days - you have tried that several times and that is what I've responded to.

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#### meijin

##### Senior Member
(This will probably be my final attempt in this thread...)

If there were only 3 days in a week (Mon-Wed) and if May 1 in the calendar above were Monday, would you call pattern 2 a pattern?

#### JulianStuart

##### Senior Member
(This will probably be my final attempt in this thread...)

If there were only 3 days in a week (Mon-Wed) and if May 1 in the calendar above were Monday, would you call pattern 2 a pattern?
Only in the (rather useless) sense of "an arrangement": there is no regularity to the interval between events. It is a schedule of events (the length of the week and the date have no bearing on this issue). The intervals between events are 3 days, 1 day, 4 days and 0 days. It's irregular, seemingly random. Are we now discussing the meaning of "pattern" or your attempt to characterize "pattern 2" as "every three days"???????

#### meijin

##### Senior Member
Julian, I had hoped I wouldn't have to do this. But please see the following revised calendars.

I think a simple YES or NO answer will be very helpful in this case. There are four "Once a week"s in the calendars. Are
2a and 2b also a "pattern" as long as you describe them as "once a week"?

Note that 2a is exactly the same as pattern 2 in the original post.

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#### JulianStuart

##### Senior Member
I'll ignore the 3-day week examples (they don't change anything under disucssion) and remind you of my earlier comment regarding 1b and 2b (they differ only in regularity, not average frequency), in case you missed it As I said anything can be a pattern so let's leave the discussions about the various possible meanings of) that word out of this - it was not an important part of the OP.
"Once a week" does not require it to be the same day each week (although it often/usually is), while (once) every seven days does require the gaps be 7 days. If it is always the same day, and that is important to the communication, one could either say every seven days or e.g., every Tuesday.
"I try to get to the gym once a week" is the kind of statement that adds imprecision enough that you might miss one week completely and that the days you are able to go may well not be the same day every week. If you want precision, you need context.

#### meijin

##### Senior Member
I give up with the following conclusion:

If there were a word called 'threenight' which means three nights (just like the word 'fortnight' that means fourteen nights), you'd say
"I go to see the doctor once a theenight" or "I go to see the doctor once every threenight". Simple as that.

#### JulianStuart

##### Senior Member
I dunno what all the fuss was about, meijin-san. Your statement does not make it clear whether you intend the meaning to be that the visits are every three days or (irregularly spaced but on average) once in each three day period (1a and 2a in #24): Post #2 made it clear that whether we talk about weeks, months, fortnights etc, the use of "once" does not make that distinction clear.If it's somewhat irregular we might well say "I go about every three days".

"Once a week" does not require it to be the same day each week (although it often/usually is), while (once) every seven days does require the gaps be 7 days. If it is always the same day, and that is important to the communication, one could either say every seven days or e.g., every Tuesday.

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#### meijin

##### Senior Member
To be honest, I don't know what's wrong with my explanations. I can't explain any better so I had to give up. It just goes to show that something super easy to understand in one language is super difficult to understand in another.

I only wanted to know how to describe pattern #2 in the example in the original post. If that's not a "pattern", then it should be a "rule". There's no "average" thing there. The visit ALWAYS happens once in each three day period. Sadly, in English there's no short and accurate way to describe that frequency. In Japanese, we say like "once in three days".

#### JulianStuart

##### Senior Member
It's the ambguity in English that must be resolved with additional words - or more specific wording. I presume that in your version "once in three days" could be either every third day or any irregular version that has one event in any given three day period (which therefore also could include more than once in any given three day period (see 2a in #24, or the "three day period of 11,12 ad 13 May" in the OP - it happens twice ). So in your version it is also ambiguous: both regular and irregular (1 and 2) in OP) are covered by the phrase?

#### meijin

##### Senior Member
Yes, you're right about that and I'm aware of it. The thing is, in Japanese we have another phrase that clearly means the regular intervals, so when the intervals are irregular, it's more likely to use the "once in three days" phrase. But there's no English equivalent for this. "Every three days" and "Once every three days" will both be interpreted as pattern 1 in the original post.

#### DonnyB

##### Sixties Mod
I apologize in advance if someone's already suggested this and it's been rejected, but I'd refer to the original "pattern 2" as "once in every three days".

So, in every consecutive three day period, you go to the doctor once, but not at regular intervals as in pattern 1.

Does that make sense?

#### meijin

##### Senior Member
Wow, is that a natural expression, Donny? Why has nobody suggested that??

#### JulianStuart

##### Senior Member
"Every three days" and "Once every three days" will LIKELY both be interpreted as pattern 1 in the original post.
In the complete absence of context, it is LIKELY to be interpreted that way but, once more with feeling and understanding
"Once a week" does not require it to be the same day* each week (although it often is), while (once) every seven days does require the gaps be 7 days. If it is always the same day, and that is important to the communication, one could either say every seven days or e.g., every Tuesday.
You can substitute month threeday, year, whatever named time interval in my bold text and it is still true. "Take one every three days" from a doctor is pretty unambiguous. "Take one in every three-day period" is not something we would expect a doctor to say.

*The gym example above contains additional wording/context to intirduce the possibiity of irregularity.

#### lingobingo

##### Senior Member
I only wanted to know how to describe pattern #2 in the example in the original post. If that's not a "pattern", then it should be a "rule". There's no "average" thing there. The visit ALWAYS happens once in each three day period. Sadly, in English there's no short and accurate way to describe that frequency. In Japanese, we say like "once in three days".
Without reading everything in this thread (life’s too short!), I would just point out that frequency, in its general sense, means the number of times something happens within a specified period — for example, once every three days. (Adding “in” makes no difference whatsoever to this meaning!) That’s all it means. In every consecutive 3-day period, this will happen once.

There is no single word the means a regular or irregular pattern of occurrences within that period.

#### meijin

##### Senior Member
In the complete absence of context, it is LIKELY to be interpreted that way but, once more with feeling and understanding
I really don't understand it. I don't know why you highlighted the first part of the first sentence below. I'd highlight the second part, as follows:
"Once a week" does not require it to be the same day each week (although it often is), while (once) every seven days does require the gaps be 7 days. If it is always the same day, and that is important to the communication, one could either say every seven days or e.g., every Tuesday.

I would just point out that frequency,
Sorry if that was the wrong word. I wondered about it but just kept typing. I've been awake all through the night so I suppose there are areas in my expressions that aren't quite right.

(Adding “in” makes no difference whatsoever to this meaning!)
Do you agree with the "(once) every seven days does require the gaps be 7 days" part of Julian's explanation? I'm really really confused...

#### JulianStuart

##### Senior Member
I don't think we will get to clarity about general definitions in the absence of anything guiding the resolution of the ambiguity (which is technically always there but usually not. The moon is full (once) every 28 days. Full moons are 28 days apart. Take a pill once every 28 days. In the strictly irregular (once in a time period) version, there is always the possibiity of twice in that same period - for some sitautions that might be a bad thing.

Let's close this loop. In the OP the question was "Does inserting "once" into the phrase help resolve the ambiguity because it has a different meaning?" I don't think so.

#### meijin

##### Senior Member
Well, I'll be back in several hours, but if my tired brain understood your posts so far correctly, it seem lingobingo thinks "(once) every three days" can mean either pattern 1 or 2, Donny thinks "(once) every three days" means only pattern 1 and he'd say "once in every three days" to describe pattern 2, and I'm not sure at all on which of the two sides Julian is.

#### lingobingo

##### Senior Member
Once every 7 days (or any set time period) means one time only within each 7-day period. Even though that does not really imply always at the same time within that period, it would be reasonable to infer that since it’s by far the most likely scenario.

Therefore, if you wanted to make it clear that something else was the case, you would have to spell that out in detail. All of which is basically what I said back in #4 (and #7).

#### meijin

##### Senior Member
Well, I hope my current understanding below is correct. (I use 2-day periods this time)

"every other day" "every second day":
These expressions will always be interpreted as 1, 3, 5, 7, 9... (if you start on day 1), and will be regarded as wrong if it was actually 1, 4, 5, 8, 9....

"(once) every two days" "Once in every two days":
These expressions will most likely be interpreted as 1, 3, 5, 7, 9..., but will NOT be regarded as wrong when it was actually 1, 4, 5, 8, 9....

"once (in) every 2-day period" "once a 2-day period"
These expressions will most likely be interpreted as a pattern like 1, 4, 5, 8, 9.... (or won't make sense at all), but it's an awkward way of explaining it or it's not correct English, so you are more likely to say "about three days a week".

Have I finally understood and explained it well?

#### lingobingo

##### Senior Member
I may have got this entirely wrong, but I see it like this…
Have I finally understood and explained it well?
In short, no. You can safely delete all the misguided conjecture you’ve written in red (and scrap “once a 2-day period”, which is unidiomatic).

We’re talking about two very different things here:

• the frequency of a particular occurrence — that is, how many times something happens during each of a consecutive series of specified time periods

• the times at which individual occurrences take place within that frequency — which may form a regular pattern, or may be irregular or even random​

There is no way of explaining both of these in a single word or phrase.

In summary, the scenarios you’ve outlined in red bear no relation to the terms you’ve highlighted in bold/green. And any assumption on the part of a listener/reader as to the regularity or otherwise of the occurrences in question would be based purely on perceived likelihood.

#### meijin

##### Senior Member
I think it would be helpful if you could tell me how you would interpret each phrase when you heard it. For example...

"every other day" "every second day":
These expressions will always be interpreted as 1, 3, 5, 7, 9... (if you start on day 1), and will be regarded as wrong if it was actually 1, 4, 5, 8, 9....
Do you agree with this? If not, why?

"(once) every two days" "Once in every two days":
These expressions will most likely be interpreted as 1, 3, 5, 7, 9..., but will NOT be regarded as wrong when it was actually 1, 4, 5, 8, 9....
How would you interpret it if I said "I jog every two days" to you? Would you think I jog like "1, 3, 5, 7, 9..." or would you think I jog "once every 2-day period"?

(and scrap “once a 2-day period”, which is unidiomatic)
I know this. That's why I said "(or won't make sense at all)".

#### lingobingo

##### Senior Member
every other day = on alternate days (a regular pattern)

If you said “I jog every two days” I would take that to mean you do so on alternate days.

#### meijin

##### Senior Member
Exactly. And that's what the first and second sections of my summary in post #38 are saying. Which means the only point we disagree is the third one. So I really don't know why you had to answer "No". (It seems you should have answered "Mostly correct".)

Anyway, I'm not saying that
"once in every 2-day period" and "about three days a week" are the same thing. I meant you'd probably answer the latter because it's more natural. But would you actually use the former expression IF you were asked to be very accurate?

Doctor: So, do you take the medicine every day or every other day?
You: Once in every 2-day period.

Finally, I've just found a site where two English teachers (at least one of them is Japanese) say "once in two days" means the same as "once every two days". I think it's wrong. "Once in two days" is grammatically correct, but native speakers wouldn't say it, right?

#### lingobingo

##### Senior Member
Once in every two days is ambiguous. It implies: at an unspecified time during either of the two days that make up each consecutive pair of days. A most odd scenario.

#### meijin

##### Senior Member
Is that a reply to my last post where I used "once in two days" (not "once in every two days") or are you referring to the the expression Donny suggested ("once in every three days")?

#### JulianStuart

##### Senior Member
Once in every two days is ambiguous. It implies: at an unspecified time during either of the two days that make up each consecutive pair of days. A most odd scenario.

#### lingobingo

##### Senior Member
Is that a reply to my last post where I used "once in two days" (not "once in every two days") or are you referring to the the expression Donny suggested ("once in every three days")?

once in two days = once in every two days / once in three days = once in every three days

The addition of “every” simply confirms that a regular pattern is meant, which is what would be assumed anyway.

But the addition of “in” has already muddied the waters/introduced ambiguity, as explained in #43.

#### meijin

##### Senior Member
OK, so I have only two questions to end this thread.

1. If I said to you "I jog every three days", you'd assume I jog like pattern 1 in the original post. How about if I said "I jog once in three days"? Would you also assume pattern 1?

2. What expression would you use in post #42 when answering that doctor's question, if you think "Once in every 2-day period" is unidiomatic?

#### JulianStuart

##### Senior Member
If I said to you "I jog every three days", you'd assume I jog like pattern 1 in the original post. How about if I said "I jog once in three days"? Would you also assume pattern 1?
As we have said a few times, in the absence of any hints, the more common situation of days 1,4,7,10 etc is the one that would likely be assumed. I think if someone said "Once in three days" I woud ask for clarification of the unusual phrase which might itself be a hint. If they were unabe to jog on a regular schedule, they might well answer with that information "I jog irregularly but about every three days or so" - that could well be enough to make someone think of "pattern 2" in the OP.

2. What expression would you use in post #42 when answering that doctor's question, if you think "Once in every 2-day period" is unidiomatic?
"Every other day" is by far most likely what the doctor wants and it is also unambiguous. A drug or treatment that could happen on consecutive days 2 and 3 (because the first is in the "2-day period" of days 1and 2 and the second in the "2-day period" of days 3 and 4) and then again in day 5 with a gap of two days is highly unlikely to be the intended dosage schedule.

#### meijin

##### Senior Member
I think if someone said "Once in three days" I woud ask for clarification of the unusual phrase which might itself be a hint.
This statement is very important/helpful. So, "once in three days" is not unidiomatic but unusual, and it implies that the speaker jogs irregularly because otherwise he would have said "I jog every three days".

"Every other day" is by far most likely what the doctor wants and it is also unambiguous. A drug or treatment that could happen on consecutive days 2 and 3 (because the first is in the "2-day period" of days 1and 2 and the second in the "2-day period" of days 3 and 4) and then again in day 5 with a gap of two days is highly unlikely to be the intended dosage schedule.
I know what you mean, but let's say you didn't follow the doctor's advice and he's asking you if you've really been taking the medicine every other day.

Doctor: Have you really been taking the medicine every other day?
You: Of course, I've been taking it once in (every) two days. (Here, you are trying to make it ambiguous. You didn't take it every other day. )

I'm really sorry to tell you that I actually have one, final question. Today I saw a website where a teacher or a dictionary said "once two days", "once three days", etc. are also correct. Really?

#### heypresto

##### Senior Member
Was it a teacher, or a dictionary? Either way they are talking nonsense.

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