The noun classic means something that's very high quality,
particularly if it has lasting value. (vocabulary.com)
- The pristine Model T Ford that you keep in your garage is a classic
Classical is the customary word when reference is made to the arts and
literature of ancient Greece and Rome (a classical scholar, classical
Latin, classical metres).
- The works studied, and also the subject itself and the study ofthe
subject, are called (the) Classics. (Fowler's Modern English usage)
Classical is also applied to serious or conventional music (i.e. that
of Beethoven, Mozart, etc.) as distinct from light or popular music;
and in physics to the concepts which preceded relativity and quantum
theory. (Fowler's....)
classic (adj.) 1610s, "of the highest class; approved as a model,"
Originally in English, "of the first class;"
meaning "belonging to standard authors of Greek and Roman antiquity"
is attested from 1620s. (etymology.com)
- Classic means 'of acknowledged excellence'
(the classic textbook on the subject),
or 'remarkably typical' (a classic case of
cerebral palsy)