置きに
Repeated at intervals, Every other, Every, At intervals of
Structure
Explanation
置きに is formed from 置き, a suffix signifying a 'gap' or 'interval', and the case marking particle に. Typically written in hiragana, this expression is used to indicate that something takes place 'every (A)' or 'at intervals of (A)'.
The distinction between interpreting this as 'every' versus 'at intervals of' can be confusing, so we will examine both meanings.
Because おきに functions as a suffix, it attaches to the end of numbers, counters, or any unit of 'space' that it is marking as a 'gap' or 'interval'.
- ジョギングは一日おきにしています。I go jogging at intervals of one day. (Every other day)
- チームのミーティングは一ヶ月おきに開かれます。The team meeting is held at intervals of one month. (Every other month)
- このパンは二日おきに焼きます。I bake this bread at intervals of two days. (Every three days)
Observing these sentences, the concept of an 'interval' can seem a bit abstract, even when translated. A simpler way to understand おきに in this usage is to think of it as 'leaving a gap of (A), then doing (B)'. So, if we say 'leaving a gap of two days, then doing (B)', it becomes more apparent that the action occurs on the third day.
Caution
It is quite common for learners to mix up ごとに and おきに. The first, ごとに, directly translates to 'every'. However, the fact that おきに can mean 'at intervals' complicates things. おきに itself will only mean 'every' in specific situations. Let's review some examples of where these two expressions have the same meaning, and where they diverge.
Large time frames or distances - Only ごとに can be used to mean 'every'. It is logical to ask 'at what point' during a day, a week, or a month an action happens. For this reason, おきに will mean 'after an interval of (A)', while ごとに simply means 'every'.
- 一日ごとにこのビタミンを飲みます。I take this vitamin every day. (The specific time of day doesn't matter, but it happens daily)
- 一日おきにこのビタミンを飲みます。I take this vitamin every other day. (We know there is an interval of one full day before it happens again)
Small time frames or distances - Both ごとに and おきに can be used to mean 'every'. It doesn't really make sense to be concerned with 'at what point' something happens during a few seconds, minutes, or hours. Here, because おきに indicates the interval, it means 'every interval of one second', etc. No one is going to ask 'when did (B) happen during the next second?', so the gap is understood as just 'one second'.
- 仕事中、２時間ごとにメールをチェックします。I check my email every two hours at work. (At some point within each two-hour block)
- 仕事中、２時間おきにメールをチェックします。I check my email every two hours at work. (After each interval of two hours. It's understood as 'every two hours' because 'when during the third hour' is not a relevant detail)
To summarize, おきに will mean 'every (A)' for seconds, minutes, hours, millimeters, centimeters, and kilometers. Conversely, it will mean 'with a space of' for nearly any unit larger than that. This is not an irregularity in the rule, but rather a shift in focus as the intervals become larger. We can just remember that おきに always serves one purpose: It highlights that (B) takes place after or outside of (A), whereas ごとに highlights (B) happening within (A).
一秒おきに - The space is 'one second'. Since おきに points to the start of the subsequent second, the effective interval is just 'one second'. Because we aren't concerned with when (B) occurs within that next second, we assume it's immediate.
五年おきに - The space is 'five years'. Since おきに points to the start of the following year, the total span becomes six years. It is natural to wonder when (B) might occur during that sixth year, so it would be odd to assume someone is acting the very instant the new year begins.
Fun Fact
This is a concept that native speakers themselves frequently get wrong, so do not feel bad if it takes some time to grasp! If you ever feel uncertain about which one to choose, it's safe to think of 置きに as 'leaving a gap of (A), then doing (B)' for most situations. 一時間 is generally the longest unit of time where people disagree about whether the meaning is 'every hour' or 'every other hour'. This makes sense, as the duration is short, but also long enough that people's perception of whether 'when' it happens is important can differ. Just remember, おきに itself only ever points to the beginning of the space after (A); it is not concerned with when or where (B) happens after that.
Examples
６時間置きに薬を飲んでいます。
I take my medicine every 6 hours.
２０メートル置きに街灯が設置されている。
There are streetlights placed every 20 meters.
一日置きにお風呂を掃除します。
I clean the bathroom every other day.
一マス置きに花を植えた。
I planted flowers in every other square.
オリンピックは４年置きに開催される。
The Olympics are held every four years.
一つ席置きに座ってください。
Please sit in every other seat.
数日置きに部長が怒る。
The department manager gets angry every few days.
ケンジ：「この植物、水やりはどのくらい？」
ユミ：「３日置きにあげれば大丈夫だよ。」
Kenji: 'How often should I water this plant?'
Yumi: 'It'll be fine if you water it every three days.'
彼は一行置きに本を読んでいる。
He's reading the book, skipping every other line.
２ヶ月置きに歯医者へ通っている。
I go to the dentist every two months.
タイルは一枚置きに色が違う。
Every other tile is a different color.
シャトルバスは１５分置きに発車します。
The shuttle bus departs every 15 minutes.