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.
The total weight or length of the genome as measured in base-pairs can be used to identify species.
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.