It is impossible to define precisely just what qualifies as an ‘underutilised species’ because of the difficulties of determining ‘proper’ or ‘correct’ levels of utilisation. In relation to these species a number of alternative qualifiers have been proposed, which emphasise certain aspects of under-use that may vary from species to species, such as:

• ‘neglected’ (by science and development),
• ‘orphan’ (without champions or crop experts),
• ‘minor’ (relative to global crops),
• ‘promising’ (for emerging markets, or because of previously unrecognised value traits),
• ‘niche’ (of marginal importance in production systems and economies), and
• ‘traditional’ (used for centuries or even millennia).

In consultation with its partners, CFF has decided to use the term “Neglected and Underutilised Species” (NUS) for species that have most or all of the following attributes:

• Unrealised potential for contributing to human welfare, in particular to:
  • income generation for the world’s poor,
  • food security and nutrition,
  • reduction of ‘hidden hunger’ (caused by the micronutrient deficiencies resulting from uniform diets that rely on a limited number of food sources);
• Strongly linked to the cultural heritage of their places of origin, or of places to which they have been introduced in the distant past;
• Long history of mainly local production or wild species whose distribution, biology, cultivation and uses are poorly documented;
• Adaptation to specific agro-ecological niches and marginal land;
• Weak or no formal seed supply systems;
• Much intra-specific diversity (landraces);
• Traditional and diverse uses and processing that vary locally
• Presence in traditional production systems with little or no external inputs, or collected from the wild;
• Receive little attention from research, extension services, farmers, policy and decision makers, donors, technology providers and consumer
• Nutritional, culinary, medicinal or other properties that are little-known or under-appreciated¹

Also, see the list of neglected and underutilised plant species².