What does sdy stand for?

Study (VRA)

Mount Marty College, Yankton, SD - OCLC symbol (OCLC)

Safe Air International, Inc. - ICAO designator (FAAC)

Sandy Corp. - AMEX symbol (SPSG)

Schenectady, NY - Amtrak rail station code

Sidney - Montana - Airport symbol (OAG)

Sidney, MT - Location identifier - FAA (FAAL)

Sunday - Telegraphy (PCTE)