NGS Style Manual‎ > ‎- S -‎ > ‎

Scot, Scottish, Scotch

Scot, Scotsman, Scotswoman:    preferred nouns—not Scotchman, Scotchwoman.

Scottish:    preferred adjective, but Scotch as in Scotch whisky, Scotch plaid, Scotch-Irish (acceptable in U.S. context).