The phenotypes of an organism are all the observable properties of the organism. These properties can be morphology, behavior or development. It can be described as the product of heredity as opposed to the heredity itself, which is called genotype. The phenotype is not always a direct product of the genotype since environment can also affect the phenotype. The genotype gives the capacity to express the phenotype. Within the field of genetics, phenotype usually means mutant phenotype. This phenotype is different from the phenotype of the wild-type, which is referred to as the normal property.
One example of a phenotype could be the color of horses' coats.
When naming phenotypes they are given three-letter names. The first letter is capitalized and the names are not italicized as the mutation names or genotypes. Superscripts are used to distinguish the mutant phenotype from that of the wild-type. For example Lac- describes an organism with a mutated lac gene that will not be able to grow on lactose as sole carbon source. The corresponding wild-type phenotype is called Lac+ and those cells are able to use lactose. A phenotype can also describe a mutation giving rise to resistance, for example RifR which describes resistance to the antibiotic rifampicin. The corresponding wild-type phenotype would be rifampicin sensitivity or RifS.