Some definitions

A dead seed is a previously viable seed that has died.

An immature seed is one that has been collected in the early days after pollination, and is not naturally fertile (although it may under specific circumstances be cultured artificially). 

A dormant seed is in a state of minimal metabolic activity. It is not able to germinate, even when environmental conditions are favourable, because something else needs to happen to break its dormancy.

A quiescent seed is a non-dormant seed that cannot germinate because environmental conditions are not favourable.

An empty seed is non-viable, because it has no ‘germ’ that is able to grow; it is not dead because it was never alive.

Regeneration is the renewal of germplasm accessions, for instance by sowing seeds then harvesting seeds from the resulting plants. The aim is to create a new generation of viable seeds, with the same characteristics as the original population.

Maintaining genetic integrity means ensuring that regenerated samples stored and distributed by a genebank are exactly the same as the original sample.

Genetic drift can occur when new generations of seeds deviate from the genotype that was originally collected, perhaps due to cross-fertilization, or contamination of seeds during threshing.