New York Consolidated Laws, Real Property Actions and Proceedings Law - RPA § 501. Adverse possession;  defined

1. Adverse possessor.  A person or entity is an “adverse possessor” of real property when the person or entity occupies real property of another person or entity with or without knowledge of the other's superior ownership rights, in a manner that would give the owner a cause of action for ejectment.

2. Acquisition of title.  An adverse possessor gains title to the occupied real property upon the expiration of the statute of limitations for an action to recover real property pursuant to subdivision (a) of section two hundred twelve of the civil practice law and rules, provided that the occupancy, as described in sections five hundred twelve and five hundred twenty-two of this article, has been adverse, under claim of right, open and notorious, continuous, exclusive, and actual.

3. Claim of right.  A claim of right means a reasonable basis for the belief that the property belongs to the adverse possessor or property owner, as the case may be.  Notwithstanding any other provision of this article, claim of right shall not be required if the owner or owners of the real property throughout the statutory period cannot be ascertained in the records of the county clerk, or the register of the county, of the county where such real property is situated, and located by reasonable means.