What is a trait called when it is controlled by more than one gene?

Hint: Genes control inherited traits and the genotype of an organism which refers to the complete set of genes found within its genome. A phenotype is a complete collection of measurable characteristics of an organism's structure and conduct.

Complete answer:
A polygenic trait is a feature, also known as a phenotype, that is influenced by a large number of genes. These genes work together to give rise to a particular trait. The inheritance of these traits is known as polygenic inheritance. Height is a classic example of this. Human height is heavily influenced by genetics, and several different genes influence height. This is why people do not grow up to be the same height as their parents.

Skin colour is another highly visible human characteristic that is influenced by a large number of genes. And this is why, despite their similarity, there are variations in skin colour between parents and children. Polygenic traits vary from Mendelian traits in which only one gene is responsible for a particular trait. Mendelian theory strictly adhered to the law of dominance.

Additional information: A Multiple allele inheritance is dominated by three or more different variants of a single gene, while polygenic inheritance is controlled by several genes.

Note: The phenotype of an individual is largely affected by the environmental factors and also the genes inherited. The body type inherited can be normal. But a person can be obese or overweight due to improper diet and lack of exercise.