My brother sometimes takes liberties with the English language- not
because he is a bad person, but rather because he simply does not know
better.  In short, he is am ignoramus with good intentions.

Recently, in a discussion about statistics, he used the word "pentile"
when I believe he meant "quintile" (i.e., one of five segments of a
distribution that has been divided into fifths).

I explained to him that the correct word is "quintile", but he got all
stubborn on me and insisted that "pentile" is a word.  After some
quick Googling, he informed me that he found researchers and Harvard
and MIT who had used the word "pentile" and that therefore, he was
correct in his usage.

A few questions for the Google Answers gurus:

1.  Is "pentile" a word in American English?

2.  Is it preferable to use "pentile" or "quintile"?

3.  In general, is my brother safe in his reasoning that "it is done
at Harvard and MIT, so it must be true?"

4.  Based solely on the information presented here, would you
characterize my brother as a "dolt"?

He and I will both be watching this space.  Please weigh in.

"Pentile," as used by your brother, is not mentioned by any dictionary
that I've consulted. The only "pentile" that I have found in a
dictionary is a misspelling of "pantile," as described in the
unabridged Oxford English Dictionary:

"pentile, mis-spelling of PANTILE, in Johnson, copied in subsequent
Dicts. (Misquoted by J. from Moxon, who has pan-tiles.)"

A pantile is a curved roofing tile. 

Your brother is obviously referring to a quintile, as you have noted.
The use of "pentile" by folks at Harvard and MIT does not, in and of
itself, make "pentile" a recognized word that is accepted by
authorities in the English language. It takes a whole lotta usage to
make a coined word like this one into a "real word." Such coinages are
more likely to gain acceptance if they define something for which
there has previously been no word. Since there is already an existing
word (quintile) that is in active use (even, I'll bet, by some people
at Harvard and MIT), the likelihood that "pentile" will make the cut
and gain the endorsement of dictionary-makers is probably slim.

I am curious: if your brother uses "pentile" instead of "quintile,"
does he turn "quartile" into "tetrile"?

I would not go so far as to characterize someone who uses the nonword
"pentile" as a dolt. I would call your brother a "neologist" (someone
who makes up words). Or I might choose a nifty term from Dr. Samuel
Johnson's 1755 masterpiece "A Dictionary of the English Language" and
call your brother a "quodlibertarian" (from the Latin "quod libet,"
meaning "what you will.")

I hope this is helpful! If anything is unclear or incomplete, please
request clarification;  I'll be glad to offer further assistance
before you rate my answer.

Best regards,
pinkfreud

pinkfreud continues to impress me with her research.  Thank you for a
fast and detailed answer.

Perhaps he ment percentile?

My brother did not mean "percentile".  He meant "one of five segments
of a distribution that has been divided into fifths".

Here's a little more color on the discussion.  My brother (let's call
him "Kevin the Neologist") was surprised to learn that I posted this
here.  While he is not averse to getting input from others, he has
concerns:

1.  Kevin the Neologist is concerned that I did not tell you that they
also use the term "pentile" within the corporate world.  Specifically,
he claims they use "pentile" at Capital One and Experian, two
organizations that are very familiar with the statistical analysis of
large datasets.

2.  Kevin the Neologist fears that I biased the discussion.  While
questions #1 and #2 are fair, he is concerned that my preamble, the
tone of question #3 and the content question #4 have made it
impossible to have a fair conversation on this issue in this forum.  I
have muddied the waters.

3.  Kevin the Neologist questions the credentials of pinkfreud-ga.  

4.  Kevin the Neologist told me that he believes something to be a
"word" if people have a common understanding of its meaning.  Because
he is aware of multiple people that share his understanding of
"pentile", it meets his definition of "word".  When I asked if
"ain't", "gonna", and "shizzle" are "words", he did not give me a
definitive answer.

5.  Kevin the Neologist claims that dictionaries are not definitive
reference sources on words.  He claims the facts that 1) my first name
is not in the dictionary, and 2) I consider my name to be a "word" are
evidence that I myself do not believe in the reliability of
dictionaries.

Given these points, it's my suspicion that Kevin the Neologist is not
viewing this issue with a clear mind.  I fear has allowed his ego,
stubbornness, and sense of fraternal competitiveness to lock himself
into an untenable position.

Thank you all for your helpfulness!

There are several references of the word pentile used in popular
scientific publications when explaining statistical groupings. Some
occur in the journal of occupational and environmental medicine.
Another is here

http://www.jwijournal.com/pt/re/jwi/abstract.00130747-200111000-00003.htm;jsessionid=D7y5ZtNlDhT4wtN0FmhWdwPn3cADQpMLjeud4uL85PkTeGobzTcB!232945895!-949856144!9001!-1

The word pentile is also a registerd trademark. So as common words can
not be trademarked one has to assume that the word did not officially
exist when the word was trademarked. The publications would indicate
that it is gaining widespread misuse. As you brother points out
Dictionaries are only a reflection of common use and hence are always
out of date???

Besides wondering about the respective ages of Bonzo and "Kevin", I
see that "PenTile matrix" is a trademarked name  - apparantly
belonging to Clairvoyante:
http://www.clairvoyante.com/pentileOverview.htm  

This seems to a be in a context that does not relate to statistics,
i.e., "quintile" could be inappropriate.

Perhaps the word pentile (adequately understandable) is used by some
statisticians in situations requiring a second type of segmentation
into five parts.
If so, this would be a special usage requiring definition in the work.
 Its use outside of this context would seem inappropriate, especially
when the reader would be expecting "quintile" and could infer that
"pentile" had a special, different meaning.
Neologisms can be fun and useful at times, but they should not confuse
the reader or listener.
I can understand "Kevin's" misgivings about the way the question has
be put, but I don't believe that biased an understanding of it. 
Suggesting that someone is an ignoramus and dolt reflects more on the
attitude of the person doing so and sounds like "fraternal
competitiveness". :)

"Kevin the Neologist" and Bonzo are free to question the reliability
of dictionaries, but to avoid misunderstanding by others, it is
helpful to accept them as definitive.
As to Pinkfreud's credentials, she has answered 1993 questions and is
recognized as one of the most savvy GA-Researchers, also for her
language skills, as I expect Bonzo also knows.
I would trust her answer.
Cheers, Myoarin

I am sorry to learn that your brother has found my work
unsatisfactory. I doubt that anything I can say will meet his needs.
He seems to subscribe to the Humpty-Dumpty theory of language.

http://www.fecundity.com/pmagnus/humpty.html

myoarin-ga writes...
>>  Besides wondering about the respective ages of Bonzo and "Kevin"...

Mid to late thirties.  Bonzo is three years older than Kevin the
Neologist.  Is this helpful?

pinkfreud-ga writes...
>>  I am sorry to learn that your brother has found my work
unsatisfactory. I doubt that anything I can say will meet his needs.
He seems to subscribe to the Humpty-Dumpty theory of language.

I think you're right, pinkfreud.  I love the link to Humpty Dumpty!  I
am grateful for your thoughtful work.

bonzo,

Thanks for the five stars and the nice tip! If you're looking for some
interesting epithets other than "dolt" when referring to your brother,
this may be of interest:

http://onelook.com/?w=*&loc=revfp2&clue=dolt

~pinkfreud

Bonzo, I didn't really expect a reply, but thanks.  I hope you two can
enjoy (note the word!) many decades of fraternal competition.  My
mother-in-law and her older sister maintained their older-younger
sister roles into their eighties, not that I am recommending this.
Myoarin

pinkfreud,

Can you please let me know how your unabridged Oxford English
Dictionary defines "word"?

Thanks,
Kevin

Kevin,

Given the circumstances, I think you should post a separate question.
It would probably be best if someone other than me answered it.

~pinkfreud

Kevin,
Of course pentile is a word; we all used it as one.  But the question
in the "subject" box was not the question asked, namely:
"1.  Is "pentile" a word in American English?"

Generally it is not, but if you found that it has been used as one
(links to Harvard and MIT?), I guess it is your privilege to go beat
on your brother until he retracts that "dolt."  ;)

I wouldn't want fraternal competitiveness to die with the settling of
this question.

Cheers, Myoarin

The discusssion lives on!  

I never meant to imply that Kevin the Neologist is a "dolt", and I
apologize for any inadvertent insinuation within Question 4. 
Candidly, I took a jab by calling him an "ignoramus with good
intentions".  This is not necessarily a bad thing, though-- consider
the (admittedly fictional) success of the Forrest Gump character!

Getting back to the original topic...   Given the thoughtful research
and intelligent comments posted here, I still believe it ill-advised
to use the word "pentile" when one clearly means "quintile".

As an interesting aside, Kevin the Neologist pronounces the word as
"PEN-tile", rhyming it with "gentile".  I wonder if others who
mistakenly use this word use other pronunciations like "PEEN-tile"
(rhymes with "penile"), "pen-TEEL" (rhymes with "Castile").

I have changed the word "pentile" to "quintile" in my presentation. 
And, I have encouraged my colleagues to begin using the word
"quintile" instead of "pentile".  In addition, I have thanked Doug for
his feedback and his help on the presentation.

But, I am more confident than ever that "pentile" is a word, which is
all that I suggested to Doug prior to his posting of this question. 
In addition, I will take Doug at his word, and will trust that his
insinuation of my being a "dolt" was truly "inadvertent".

Also, I am glad that we got things cleared up before Thursday.... as,
I didn't want everything to be too uncomfortable around the
Thanksgiving table. : )

Kevin

I have been reading "pentile" like gentile all along.

I hope you each get a drumstick!

After all that, Kevin the Neologist's position is that "I never said
that it was proper to use 'pentile'.  I merely said it was a 'word'."

How disingenuous.  As if he expected ANYONE to deny that "pentile" is
"a sound or a combination of sounds that symbolizes and communicates a
meaning."

Sigh.  With a sibling this petty, it's not hard to see why I'm not
really looking forward to Thanksgiving.  Of course, he really hasn't
been himself since the accident, so I'll cut the little fella some
slack.