For those who may not be familiar with Melville:
Melville is a hamlet (an unincorporated area) in the southwest part of the Town of Huntington, in the west part of Suffolk County, along the Huntington/Babylon town line and the Huntington/Oyster Bay town line, and the Suffolk/Nassau county line.
Beginning on the north and moving in a clockwise direction, the Hamlet of Melville in the Town of Huntington is bordered on the north by the Hamlet of West Hills and the Hamlet of South Huntington; on the east by the Hamlet of Dix Hills; on the south by the Hamlet of Wheatley Heights, the Hamlet of Wyandanch and the Hamlet of East Farmingdale in the Town of Babylon (the Huntington/Babylon town line); and, on the west by the Hamlet of Old Bethpage and the Hamlet of Plainview in the Town of Oyster Bay, Nassau County (the Huntington/Oyster Bay town line and the Suffolk/Nassau county line).
The Hamlet of Melville has a different border than does the "Melville, NY 11747" ZIP Code postal zone (i.e., a place can have a "Melville, NY 11747" mailing address and not be in the Hamlet of Melville and a place can have other than a "Melville, NY 11747" mailing address and be in the Hamlet of Melville): places that have a "Melville, NY 11747" mailing address that are not in the Hamlet of Melville are in the Hamlet of West Hills, the Hamlet of South Huntington, the Hamlet of Wheatley Heights and the Hamlet of Wyandanch; and, at the same time, there are places in the Hamlet of Melville with a "Wyandanch, NY 11798" mailing address.
For a good set of town-by-town maps showing all the villages and hamlets in each of LI's 13 towns (3 in Nassau County and 10 in Suffolk County):
Excellent Long Island Geographic Resource