Distinguish between monogenic & polygenic inheritance ... ?

"Mono" means one, and "poly" means many, so monogenic would be once gene inheritance, and polygenic would be multiple gene inheritance.

Monogenic InheritanceTheir expression of trait produces discontinuous variation. The complete trait was expressed by a dominant allele. Qualitative traits are controlled by monogenic inheritance. Dominant parent and F1 individuals are similar.

Polygenic inheritanceContinuous variations in the expression of a trait are produced by polygenes. Unlike monogenic, just a single dominant allele expresses only a unit of the trait of a polygenic. Either quantitative or metric trait was controlled by polygenic inheritance. One to several pairs of alleles is representing a character. The dominant genes have increased effect on the expression of the trait. There is more intermediate form. Individuals with the dominant trait are usually as few like recessive trait.