Dichotomous Key
/dy-KOT-oh-mus kee/🏷️ Taxonomy●● Intermediate
Also known as: identification key, botanical key
A dichotomous key is a hierarchical identification tool that presents a series of paired contrasting statements (couplets) about observable characteristics. At each step, the user chooses which statement best fits the specimen, which leads to either an identification or another couplet. For plants, couplets might distinguish leaf arrangement (alternate vs. opposite), flower symmetry (radial vs. bilateral), or fruit type (dry vs. fleshy).
Etymology
From Greek dichotomia (dividing in two) + Old English cæg (key, solution)
Example
“Using the dichotomous key, students identified the unknown tree by working through leaf, bark, and fruit characteristics.”