Forgery is the act of creating a false version of something. The false version is also referred to as a forgery.
Common targets for forgers include:
Many experts and systems are in place to reduce losses due to forgery. Usually if the forgery is of something that should be old (like a painting), experts can examine the materials used to determine if they date from the correct era. Systems in familiar use are the complex ways that paper money is designed to be difficult to counterfeit, and the special markers retail clerks can use to determine the genuineness of higher denomination bills when presented.