1

One can use the terms primary, secondary, and tertiary to describe the first, second, and third levels of something.

What would the fourth level be called? Would it be something like "quartiary" or "quartenary"? How about the fifth level?

2

Fourth level: "quaternary"

1 a : of, relating to, or consisting of four units or members
http://www.merriam-webster.com/dictionary/quaternary

Fifth level: "quinary"

1. pertaining to or consisting of five.
http://dictionary.reference.com/browse/quinary

  • In protein structure: "Globular and fibrous proteins may exhibit one or more of four types of protein structure. These structure types are called primary, secondary, tertiary, and quaternary structure." – DJohnM Aug 15 '14 at 20:30

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