Naming Nine Things

Date: 01/15/2003 at 09:41:22
From: Connie P. (Middle School Math teacher)
Subject: Naming nine things (like 3 is triplet)

What is the correct name for nine things collectively?  I can only 
fine the answer up to 7, septuplet, which has been highly publicized 
with the McCoy babies. I am guessing nonet because non as in nonagon 
represents a nine-sided figure.

Date: 01/15/2003 at 10:16:48
From: Doctor Peterson
Subject: Re: Naming nine things (like 3 is triplet)

Hi, Connie.

You've got the right basic idea, though our FAQ lists enneagon rather 
than nonagon, because "non-" is the Latin prefix for 9 while "ennea-" 
is the Greek prefix, which fits better with the Greek "-gon".

My dictionary (American Heritage) lists "octuple," "nonuple," and 
"decuple," so the natural thing is to add a "t" to each to make the 
form you want for a set of babies:

    triplet
    quadruplet
    quintuplet
    sextuplet
    septuplet
    octuplet
    nonuplet
    decuplet

I notice my dictionary doesn't even list "septuplet," probably 
because there hadn't been any when it was published; but "sextuplet" 
is listed as formed by combining "sextuple" with the ending of 
"triplet," supporting this assumption. Even m-w.com lists only up to 
sextuplet, and it doesn't include octuple or nonuple but does have 
decuple.

In math, the corresponding term would just be "9-tuple"; why use 
words when numbers will do? In music, you would use "sextet,"
"septet," "octet," "nonet"; these are all listed in m-w.com.

If you have any further questions, feel free to write back.

- Doctor Peterson, The Math Forum
  http://mathforum.org/dr.math/