Background: In my line of work, we test samples from certain rivers each year. However, if we tested samples from river x and river y this year, we will leave them out of our sample selection over the next 2 years. That way we do not end up testing any river for consecutive years.

What term best describes this selection method? I have come up with a periodic selection and rotational selection. Are there better words to convey the message?

Thank you.

4 Answers 4


Maybe it's better to explicitly state what is being avoided, such as you did in your first paragraph. There may be words that convey the meaning but that are not as exact. For example, there are a variety of farming terms such as "leave fallow" and a bunch of things like that. These are likely to be inexact and lead to misunderstandings.

Something along the lines of "avoiding sampling the same place two years in a row" might be clunky, long, and awkward, but it seems important to get the entire idea.

  • Yes what you said makes sense. Thank you. Nov 26, 2019 at 17:43
  • I'm guessing that the two people who down-voted did so because I didn't provide a single word to the single word request. Considering that the person who asked the question has marked my answer as accepted, it seems kind of beside-the-point to do so without at least saying why.
    – puppetsock
    Nov 27, 2019 at 18:48
  • Advice that doesn't address the question correctly (and note that stricter adherence to site rules may penalise other contributors) can be given in 'comments'. This answer is hardly what is expected on a site aimed at linguists. Nov 27, 2019 at 19:06

If you omit them for two years, then it means you test them every third year, so triennial might work. If it's not always going to be spaced like that, then periodic is descriptive but flexible. Rotational is good too, if you want to suggest a repeating order: z,y,z,x,y,z, etc.

  • Thanks for the feedback. However, it is not the case that we will certainly test them every third year. All we are doing is to avoid selecting them for the next 2 years if we happen to test them this year. Nov 27, 2019 at 8:44

If all you want to say is that one thing is not tested twice in a row, then you could use the implied word from the question itself: nonconsecutive.

[Merriam-Webster] : not being in a sequence : not consecutive
// Exercise three times a week on nonconsecutive days.

Possible sentences from the question include the following:

River X is a nonconsecutive selection.
We use a nonconsecutive schedule for our testing.

If you want to emphasize a particular sense of repetition, you could use cyclic (or cyclical):

1 a : of, relating to, or being a cycle
// cyclic changes in the weather
// the cyclical nature of history

1 : an interval of time during which a sequence of a recurring succession of events or phenomena is completed
// a 4-year cycle of growth and development
2 a : a course or series of events or operations that recur regularly and usually lead back to the starting point
// … the common cycle of birth, growth, senescence, and death.
— T. C. Schneirla and Gerard Piel

Possible sentences from the question include the following:

River X is a cyclic selection.
We use a cyclical schedule for our testing.


Systems that are essentially random, but which exclude items selected earlier within a specified time window are quite common. Jury duty in the US is one example. I also worked on a communications system that "locked out" the previous message channel to ensure the entire network was operating properly (and to subvert spoofing attempts).

In the recent context of reality television, this is called immunity. For jury duty, the term is exemption, and for electronics, the term is locked out.

The general term is exclusionary

causing someone or something not to be allowed to take part in an activity or to enter a place:


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