In biology, determination is the process of matching a specimen or sample of an organism to a known taxon, for example identifying a plant as belonging to a particular species.
Modern tools include single or multi-access identification keys, which can be printed or computer-assisted.
Determination then requires comparisons of certain characteristics and then assigning a particular specimen to a known taxonomic group, hopefully ultimately arriving at a species or infraspecific name.
Using DNA barcoding is a modern method that does not require the determiner to be highly trained.
In forestry, especially in the tropics, identifying trees based on the flowers or leaves high up in the crown can be difficult, a method of identifying tree species in this case is called a 'slash', a shallow machete cut to the trunk to expose the colours of the different layers inside, and show the type of sap.
Projects like iNaturalist and Pl@ntNet relies on crowdsourced data and assists identification through automatic as well as community input.