What is the term for the observable characteristics of an organism?

The term for the observable characteristics of an organism is phenotype. It includes features such as height, flower color, blood type, body shape, physiological measurements, and behavior.

A phenotype develops through the interaction of an organism’s genotype—the alleles it carries—with environmental influences. For example, genes affect a person’s potential height, while nutrition and health during development can affect the height ultimately observed. Phenotypes can also change during an organism’s life without any change to its DNA.

The word is commonly confused with genotype. Genotype refers to genetic makeup, whereas phenotype refers to the traits expressed or observed. Two organisms can have different genotypes but a similar phenotype, such as two pea plants with purple flowers, or the same genotype can produce somewhat different phenotypes under different environmental conditions.

In modern biology, phenotype is broader than outward appearance alone. Traits detectable through laboratory tests, including blood-group chemistry or patterns of gene expression, may also be considered phenotypic characteristics.