What is "classicals orders"

Classic \Clas"sic\ (kl[a^]s"s[i^]k), Classical \Clas"sic*al\, a. [L. classicus relating to the classes of the Roman people, and especially to the frist class; hence, of the first rank, superior, from classis class: cf. F. classique. See Class, n.]

1. Of or relating to the first class or rank, especially in literature or art.

   Give, as thy last memorial to the age, One classic drama, and reform the stage.
   --Byron.

   Mr. Greaves may justly be reckoned a classical author on this subject [Roman weights and coins].
   --Arbuthnot.

2. Of or pertaining to the ancient Greeks and Romans, esp. to Greek or Roman authors of the highest rank, or of the period when their best literature was produced; of or pertaining to places inhabited by the ancient Greeks and Romans, or rendered famous by their deeds.

   Though throned midst Latium's classic plains.
   --Mrs. Hemans.

   The epithet classical, as applied to ancient authors, is determined less by the purity of their style than by the period at which they wrote.
   --Brande & C.

   He [Atterbury] directed the classical studies of the undergraduates of his college.
   --Macaulay.

3. Conforming to the best authority in literature and art; chaste; pure; refined; as, a classical style.

   Classical, provincial, and national synods.
   --Macaulay.

   Classicals orders. (Arch.) See under Order.