Is "lustrum" (pl. lustra) an understandable (say, at least in academic publications) or valid/common term for a five year span, e.g. to use in a table summarizing data where space can be very valuable? In other words:

  • Is "lustrum" archaic?
  • Is "pentad" an alternative?
  • 2
    'five years' is what one normally uses in English.
    – Mitch
    Jul 29, 2012 at 22:53
  • 1
    How about quincade?
    – Pitarou
    Jul 30, 2012 at 13:14
  • @Pitarou, decade is from Greek, so it should be pentad, which is also in the OED.
    – Toothrot
    Nov 14, 2019 at 2:25

2 Answers 2


This website says the last lustrum was held in a.d. 74 by Vespasian. So I would say, no, lustrum is not the word you're looking for. Pentad is not in some dictionaries, and the one I found that does have it defines it as "a group of five". So that's not the word you're looking for, either. I would suggest

5 yr span

if you're trying to squeeze it into as short a space as possible. Quinquennium does mean what you want it to, but it's quite rare and fairly long.

  • 5
    @Tim: Well, if Lustrum was also the name of a recent Academy Award-winning film, it sure would help. Jun 8, 2011 at 0:21
  • 2
    I'm going to work "quinquennium" into a conversation soon. Jun 8, 2011 at 1:53
  • 1
    Diving into ngrams, lustrum is apparently not as rare as I’d thought: here, compare it with another somewhat arbitrary selection of words. However, I share with other answerers the feeling that few English speakers would understand it (especially without a clarifying context).
    – PLL
    Jun 8, 2011 at 5:38
  • 2
    Pentad has the advantage that people are more likely to be able to guess at least the five part of the meaning (by analogy with pentagon, pentagram and other words of similar Greek origin). Lustrum would leave me guessing.
    – psmears
    Jun 8, 2011 at 11:39
  • 1
    @PeterShor, good point! but I think you'll find it's chiliad.
    – Toothrot
    Nov 14, 2019 at 13:18

The word you are looking for is "demi-decade".

Somebody sent me a message saying that people likely needed a citation to a dictionary or the like to validate my response in some unspecified way. I'm not sure I understand that, as the imminent good sense of the response seems to me to be fairly self-evident.

Nevertheless, if any of you feels the need for additional "authority" from Captain Obvious, please consult the English language dictionary of your choice to see that "demi" means half (as in "demisemiquaver", from the Latin "dimidius", which means to be "cut in half/through the middle"), and "decade" means ten years.

You do the math...


  • Bart, it would be best to not use all caps in a response. I think I would edit the answer. And, you would do well to provide a source, such as a dictionary, to validate your answer. Thanks.
    – J. Taylor
    Nov 13, 2019 at 22:29
  • Pointing out that there are separate dictionary entries for the two components of the word is not the same as showing that the word itself is in general use. As has been observed at www.macmillandictionary.com/buzzword/entries/demi-decade.html, 'the word demi-decade, though perfectly transparent and useful, is yet to be acknowledged by mainstream dictionaries. It's an interesting example of a concept which seems completely obvious, but for which we've been slow to adopt a specific moniker'.
    – jsw29
    Nov 15, 2019 at 1:10

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