|Look up third party in Wiktionary, the free dictionary.|
In commerce, a "third-party source" means a supplier (or service provider) who is not directly controlled by either the seller (first party) or the customer/buyer (second party) in a business transaction. The third party is considered independent from the other two, even if hired by them, because not all control is vested in that connection. There can be multiple third-party sources with respect to a given transaction, between the first and second parties. A second-party source would be under direct control of the second party in the transaction.[dead link]
In Information Technology, a "third-party source" is a supplier of software (or a computer accessory) which is independent of the supplier and customer of the major computer product(s).
There are other uses of the term "third-party source" as well.