A dichotomous key is a tool used in taxonomy and identification to classify organisms based on a series of sequential questions or statements that present two contrasting options. Den følger en trin-for-trin-proces med eliminering, som giver brugerne mulighed for at indsnævre de mulige kategorier eller grupper, som en organisme tilhører.

Dichotomous keys are often presented as a series of paired statements or questions, with each pair providing two options that contrast with each other. Brugeren starter ved det første par og vælger det udsagn eller den mulighed, der bedst beskriver organismen. Dette valg fører derefter til det næste par udsagn eller spørgsmål, som yderligere forfiner klassifikationen.

Processen fortsætter, indtil brugeren når frem til en erklæring, der unikt identificerer organismen eller placerer den i en bestemt taksonomisk kategori. Hvert trin i nøglen er med til at eliminere muligheder, der ikke gælder, og guider brugeren mod den korrekte identifikation.

Dichotomous keys are widely used in various fields of biology and taxonomy, such as botany, zoology, and microbiology, to classify and identify species based on their characteristics and observable traits. They are particularly useful for identifying organisms that cannot be easily distinguished by a single characteristic or that have many similar species.

The simplicity and logical structure of dichotomous keys make them accessible to users with different levels of expertise, allowing for standardized and efficient identification of organisms. They are commonly employed in field guides, identification manuals, and scientific publications to facilitate accurate and consistent species identification.