(Terms are as used by the Willamette Partnership.)

Additionality: the concept that calls for credited ecosystem improvements to represent an overall increase in, or avoided reduction of, ecosystem services, relative to those services that would have existed without creating the credits.

Aggregator: a person or institution that solicits, combines and/or markets ecosystem service credits from multiple sources on behalf of the credit owners. An aggregator facilitates financial transactions between the buyers and sellers of credits, and may charge a fee for the service, but is not directly involved in the chain of ownership of credits.

Broker: a licensed person or institution that buys and sells ecosystem service credits, or facilitates financial transactions between the buyers and sellers of credits. Brokers can be directly involved in the chain of ownership of credits.

Bundling or stacking credits: the creation of different credit types in the same geographic area. It allows landowners to market multiple ecological values at a single site, including those with and without specific geographic delineation.

Common currency market: allows for the generation and trade of a single, universal credit (such as an "ecosystem credit") that captures the value of broad ecological functions and values, through an agreed upon accounting tool, within a defined service area.

Credit: a single unit of trade that quantifies the provision (or right of use) of a regulated or non-regulated ecosystem service.

Exchange: an institution that inventories and accounts for all of the different credits available within a market or a marketplace by documenting their generation, ownership, and trade. An exchange generally requires credit traders to pass some sort of legitimacy or competency test prior to participation.

Multi-credit marketplace: a market that allows for the generation and trade of multiple ecological values.

Payments for ecosystem services: refers to the diversified portfolio of payments that can be gathered by a single landowner or manager for actions taken on a site. Income may be derived from the sale of certified products, like lumber, from incentive programs, and/or from the sale of credits in an ecosystem marketplace.

Single-credit market: a market that allows for the generation and trade of one credit type.

Verifier: a person or institution that confirms actions taken on the landscape produce the desired ecological benefits necessary for credit creation.