As an adjective quintessential
is of the nature of a quintessence (in all senses); ultimate.
As a noun idiosyncracy is
an alternative spelling of lang=en.
idiosyncracy
English
Noun
(idiosyncracies)
Usage notes
* This spelling is commonly considered a misspelling; etymologically the preferred spelling is idiosyncrasy'', which is also the only spelling given by most dictionaries, such as the ''Dictionary.com Unabridged'' gives both spellings, but under the entry name ''idiosyncrasy .
References