Define phenotype.

Hint: The terms phenotype and genotype are most commonly used in genetics to describe an individual trait. Traits are nothing but the characters which are inherited and are usually affected by both genotype and phenotype. These terms may sound similar but there are distinguishing characters between them. The term phenotype was introduced by Wilhelm Ludvig Johannsen to explain about the external characteristics of an organism.

Complete answer:
Getting into the details, the term phenotype denotes the physical appearance i.e. the external characters of an organism which are visible. To make you clear the height, hair color of a person or seed color, seed shape of a plant are examples of phenotype. The phenotype doesn't inherit from the parent to offspring whereas the genotype is the genetic makeup of an organism. Every character such as skin tone, weight, height etc contains genes for it in the form of DNA. These genotypes and phenotypes together influence the appearance of an organism. The phenotype depends upon which genes are dominant and expressed. The phenotype of an organism is affected by its genetic expression i.e. the genotype and also the surrounding environmental conditions. Both factors combine together to give a specific phenotype to the organism.

Note:
In Mendel's monohybrid cross, the phenotypic ratio is 3:1 whereas the genotypic ratio is 1:2:1. Phenotypic ratio is 3:1 because when TT and Tt are observed from an external view, they denote tallness but when you observe its genotype Tt is heterozygous containing genes for tall and dwarf but the outcome is tall because the gene for tallness is dominant.