During the introduction stage of the product life cycle, promotional expenditures are made to stimulate consumer desire for an entire product class rather than for a specific brand. the consumer desire that is stimulated is referred to as demand. during the growth stage of the product life cycle, promotional expenditures are made to stimulate consumer desire for a specific brand due to increased competition. the consumer desire that is stimulated is referred to as demand.

During the introduction stage of the product life cycle, promotional expenditures are made to stimulate consumer desire for an entire product class rather than for a specific brand. The consumer desire that is stimulated is referred to as primary demand.
Primary demand is the desire for a product class rather than for a specific brand.During the growth stage of the product life cycle, promotional expenditures are made to stimulate consumer desire for a specific brand due to increased competition. The consumer desire that is stimulated is referred to as selective demand.Selective demand is the preference for a specific brand.

The  atomic nucleus  is the small, dense region consisting of  protons  and  neutrons  at the center of an  atom, discovered in 1911 by  ernest rutherford based on the 1909  gold foil experiment.