Short for ‘environmental DNA’. Refers to DNA deposited in the environment through excretion, shedding, mucous secretions, saliva etc. This can be collected in environmental samples (e.g. water, sediment) and used to identify the organisms that it originated from. eDNA in water is broken down by environmental processes over a period of days to weeks. It can travel some distance from the point at which it was released from the organism, particularly in running water. eDNA in soil can bind to organic particles and persist for a very long time (sometimes hundreds or thousands of years). eDNA is sampled in low concentrations and can be degraded (i.e. broken into short fragments), which limits the analysis options.