of or relating to or characteristic of Scotland or its people or culture or its English dialect or Gaelic language
Scots Gaelic
the Scots community in New York
`Scottish' tends to be the more formal term as in `The Scottish Symphony' or `Scottish authors' or `Scottish mountains'
`Scotch' is in disfavor with Scottish people and is used primarily outside Scotland except in such frozen phrases as `Scotch broth' or `Scotch whiskey' or `Scotch plaid'