Heredity refers to the genotype(genetic makeup) of an organism. The study of heredity is called genetics and Gregor Mendel is considered to be a founder of this branch of science. He worked with the garden pea and did years of research involving traits like height, seed shape and flower color, among others. By keeping careful records, he was able to discover certain Principles of Heredity-Dominance, Law of Segregation and Principle of Independent Assortment. This was all done in the 1800's when knowlege of the gene did not exist and he termed the characteristics passed down from parent to offspring--factors or traits. We now know that genes are passed down from parents to offspring through their gametes which contain half of the DNA the future offspring will inherit. Through fertilization, the full complement of DNA is inherited by the offspring and this diploid set of chromosomes is what determines the organism's heredity.
the definetion of heredity is the passing on of features from parents to offspring by means of genes :)