I was curious to know what comes after:

Primary, secondary, tertiary, ...

This Oxford website says it is "quartenary, quinary, ..."

But they are already taken!

Unary, binary, ternary, quaternary, quinary, ...

And according to this EL&U post deriving from the Latin originals should give:

Primary, secondary, tertiary, quartary, quintary, ...

Wiktionary says that "quartary" (from the ordinal) is correct, but "quaternary" (from the distributive number) is common especially in biology.

So, what should it really be in English?

  • I've never heard of quartary or quintary, only quaternary which is about as high as I would expect people to know. After that, we just use the English ordinals, 5th, 6th &c. – JDF Jan 24 '18 at 12:30
  • @Deonyi: The words "first, second, third" do not mean the same as "primary, secondary, tertiary". We can say "the primary reason for X is Y" to mean "the most important/significant reason for X is Y", whereas "first" will not be suitable for this. – user21820 Jan 24 '18 at 14:46
  • Yes, but after quaternary their meanings blur. This happens even lower, however you have to use a construction like 'the first and foremost'. – JDF Jan 25 '18 at 5:21
  • @Deonyi: Well the fact that you use "foremost" shows that "first" does not work there. And there is no similar construction for "secondary". – user21820 Jan 25 '18 at 8:36

Logically it should be "quartary" because the Latin is "third" = "tertius"; "fourth" = "quartus"

In the first, we deleted the "us," hence "quartary."

I can see a 1773 publication in the search results for "quartary" that uses the word: https://books.google.com/books?id=1-UEAAAAQAAJ

  • Thanks a lot for sharing your finding! The first page uses both "tertiary" and "quartary" in the same sentence, with the meaning I am looking for. – user21820 Feb 23 '18 at 8:45
  • @user21820 It hasn't been 1731 for quite some time now. Quartary, quintary, etc. are obsolete. As per Deonyi's comment to OP, current usage is "quaternary" (or even just "fourth"), then the regular English ordinals. – Spencer Feb 23 '18 at 10:18
  • Extremely rare. Quaternary is the common term instead. – Kris Feb 23 '18 at 10:51

In a science context, the next term would be Quaternary Structure.

http://www.particlesciences.com/news/technical-briefs/2009/protein-structure.html is where is got this from.

I am not sure about what comes after this.

  • Yeap I'm aware of the use of "quaternary structure" in biology, as stated in my question. =) – user21820 Feb 14 '18 at 11:37

Here is something I was able to discover on the internet the prime time I confronted the same predicament as you.

  • 1st = primary
  • 2nd = secondary
  • 3rd = tertiary
  • 4th = quaternary
  • 5th = quinary
  • 6th = senary
  • 7th = septenary
  • 8th = octonary
  • 9th = nonary
  • 10th = denary
  • 12th = duodenary
  • 20th = vigenary.

These come from the Latin roots. The -n- ones come as well from Latin but this time are distributive adjectives, "one each, two each, etc."; they are always used in plural. They were sometimes also used in a sense roughly similar to the ordinals, which is probably why English uses them in an odd way.

  1. (Singuli — single "one each")
  2. Bini — binary "two each"
  3. Terni/trini — ternary/*trinary
  4. Quaterni — quaternary
  5. Quini — quinary
  6. Seni — senary
  7. Septeni — septenary
  8. Octoni — octonary
  9. Noveni — *novenary
  10. Deni — denary
  11. Undeni — *undenary
  12. Duodeni — duodenary
  13. Terni/trini deni — *ternidenary/*tridenary
  • 1
    Does the second list come from the EL&U post I cited in my question? If so, you should state your source. – user21820 Feb 14 '18 at 11:39

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