What are the three orders in Ancient Greek architecture?

The three
orders in Ancient Greek architecture are Corinthian, Doric, and Ionic. These architectural
classifications have been used since the first century B.C., when the Romans adopted these
orders as part of their architectural system. These orders are generally used to define and
describe all neo-classical European architecture.

• Corinthian order
  - these columns, the most ornate of the three, are slender and fluted, decorated with several
  rows of acanthus leaves and scrolls.
• Doric order - these columns are the
  "oldest, simplest, and most massive" of the three orders; they are fluted with a round
  base (though often they are free-standing) and a square top.
• Ionic order -
  these columns are taller and thinner than Doric columns and are recognizable by the two scrolls
  at the top.

Both links below have drawings and diagrams of each
order of columns. 

href="https://en.wikipedia.org/wiki/Classical_order">https://en.wikipedia.org/wiki/Classical_order
href="https://www.dummies.com/education/architecture/greek-architecture-doric-ionic-or-corinthian/">https://www.dummies.com/education/architecture/greek-arch...