I was familiar with the word 'arboretum', a plantation of trees for ornamental or scientific purposes, but not with 'pinetum' which I heard for the first time yesterday. Then I discovered 'coniferetum'.

The OED tells me of the -etum suffix :

Forming nouns denoting a collection or plantation of plants

I cannot remember any other English words carrying the same suffix and I would be interested to learn why there is this speciality in English.

  • Since it appears to be taken from the identical Latin suffix, which also denoted plantations and gardens, it would seem that it likely is. Unless you’re asking whether it’s only trees specifically, and not bushes or flowers or other plants, in which case I have no idea. Arboretum is the only one I’ve ever heard of, too. – Janus Bahs Jacquet Feb 17 '18 at 20:13
  • 'Ashley's Backwards Phonemes' lists, for words ending in -etum, at least tapetum / pinetum / ombretum / sulphuretum / arboretum / catasetum / fruticetum / equisetum / alicetum. You can check these for yourself. Not all words ending in a certain string need have the same (or necessarily any) suffix. – Edwin Ashworth Feb 17 '18 at 21:30
  • It was mentioned on BBC radio today that the word 'arboretum' was coined in 1840 by John Claudius Loudon who designed the one in my home city of Derby, Britain's first purpose-'built' public park. – Kate Bunting Feb 18 '18 at 18:10

You can find all the words in the OED ending in this sequence of letters by searching for *etum.

For those of you without access to OED, this site would also work, but it uses a different syntax (regex), which is harder to use but is ultimately more powerful; you'd want to search for etum$.

By doing such a search, it is possible to find words such as:

  • decretum
  • tapetum
  • secretum
  • acetum
  • papaveretum *
  • quinetum *

However none of the above are formed from the -etum (plant) suffix you are asking about (the words marked with * are formed with a different -etum suffix, from the word acetum). There are several words I found that use the -etum (plant) suffix that are about plants, but not trees:

  • fruticetum: "a collection of shrubs" (etymology: "Latin fruticetum a place full of shrubs or bushes, < frutex shrub, bush") — OED
  • filicetum: "a collection of living ferns" — OED

I was able to find one word using the -etum (plant) suffix that is not related to plants at all:

  • sulphuretum: "an ecological community of organisms, mainly consisting of sulphur bacteria, which metabolizes sulphur compounds in a closed subcycle of the larger environmental sulphur cycle." — OED
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  • More importantly, is it the same etymologically? – marcellothearcane Feb 17 '18 at 21:09
  • @marcellothearcane What are you specifically asking about? I'll be glad to clarify if I know what I'm clarifying ;) – Laurel Feb 17 '18 at 21:28
  • For example, is the -etum from secretum derived from the same root as arboretum? The OP has included the etymology tag... – marcellothearcane Feb 17 '18 at 21:34
  • Re-reading it though, you have talked about the -etum (plant) suffix. That's basically what I'm saying, is it not? :) – marcellothearcane Feb 17 '18 at 21:35
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    @marcellothearcane Secretum (and the other items) in that list do not use the -etum suffix; most of them are from Latin and the rest (marked with asterisks) are derived from acetum. The other word, sulphuretum, is derived from the -etum (plant) suffix asked about in the OP. – Laurel Feb 17 '18 at 21:39

It may not be exclusive to tree plantations. Fruticetum is a kind of arboretum featuring shrubs and bushes rather than trees. wiktionary

Wiktionary lists 60 such latin -etum.

Here though is a list of 18 in english: 18 english words ending in -etum

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  • 2
    The Wikipedia page lists 60 Latin words, but it seems like most of them are not used in English. (Sepulcretum doesn't seem to be used in English either.) – Laurel Feb 17 '18 at 20:47
  • @Laurel - noted! I will so edit my answer. – lbf Feb 17 '18 at 21:04
  • 'Sepulcretum' itself is Latin, not English, as Laurel stated. It needs editing out. – Edwin Ashworth Feb 17 '18 at 21:32

I think there are only a few rare words like acetum:

a preparation having vinegar or dilute acetic acid as the solvent.


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  • 3
    Isn't acetum just an example of a word that ends in the letters E T U M and the sound /ˈiːtəm/? I don't think it actually contains any suffix -etum, much less the same suffix as words like arboretum. – herisson Feb 17 '18 at 20:37
  • 1
    acetum is acet[ic] + [-i]um, not ac[-] + [-]etum. – Nij Feb 18 '18 at 0:08

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