Freshwater ecosystems, also referred to as freshwater wetlands, comprise many different types, geomorphic forms and sizes and have been defined and classified in different ways, although not all efforts are systematic or readily comparable. Differences in definitions and classification have presented some practical difficulty in determining the distribution and extent of freshwater wetlands despite the large effort directed at wetland inventory globally. Wetlands are found on all continents and global mapping initiatives have documented the latitudinal and longitudinal distribution of area as well as displayed a general distribution of wetland types. Whilst usage of the term 'wetland' has increased in recent decades there is a diversity of terms that have been used to describe freshwater ecosystems, including those in the Ramsar Convention's definition and classification of wetland types. Even common terms used by the scientific community can signify different wetland types due to regional or continental norms of usage.