How do you say "once every x days/weeks/etc"?


Could anyone help me with this translation? I think once per week is "shuu
ichi" but with days in particular I really don't remember how to say it.




The most generic and useful pattern is `number + counter + に + number + 回/度`.

  * 2年に1回 once in two years
  * 6週間に1回 once in six weeks
  * [1月]{ひとつき}に3回 ／ [1か月]{いっかげつ}に3回 three times a month
  * 1年に2回 twice a year
  * [1日]{いちにち}に3回 three times a day
  * [2日]{ふつか}に3回 three times in two days

There are some irregular readings when referring to a time span. See the last
part of [this page](http://www.guidetojapanese.org/learn/complete/date_time).

You can also say 日【ひ】にn回, 週(に)n回, 月【つき】(に)n回, 年(に)n回 (but not 時間n回, 日n回, 週間n回,
etc).

>   * 1週間に5回バイトをする = 週(に)5回バイトをする to work part-time five days a week
>   * 年(に)1度の総会 the annual general meeting
>

週一【しゅういち】 is a bit slangy and colloquial phrase that means 1週間に1回 (once a
week). You can also say 週一【しゅういち】 ～ 週七【しゅうなな】, 月一【つきいち】, 年一【ねんいち】. (But
月三/年四/etc are rare and you should usually say 月に3回/年4回 instead)

>   * 週七【しゅうなな】でバイトをする to work part-time seven days a week
>   * 月一【つきいち】のミーティング monthly meeting
>

In addition, there are 隔日【かくじつ】, 隔週【かくしゅう】, 隔月【かくげつ】, 隔年【かくねん】 which mean
"every other ～".

> 隔週のミーティング biweekly meeting

