1.(product development definition) (from biology) The four stages that a new product is thought to go through from birth to death: introductory, growth, maturity, and decline. Controversy surrounds whether products do indeed go through such cycles in any systematic, predictable way. The product life cycle concept is primarily applicable to product forms, less to product classes, and very poorly to individual brands. 2. (strategic marketing definition) This describes the stages in the sales history of a product. The product life cycle (PLC) has four premises: (1) that products have a limited life; (2) that product sales pass through distinct stages, each stage having different implications for the seller; (3) that profits from the product vary at different stages in the life cycle; and (4) that products require different strategies at different stages of the life cycle. The product life cycle has four stages: (1) introduction-the slow sales growth that follows the introduction of a new product; (2) growth-the rapid sales growth that accompanies product acceptance; (3) maturity-the plateauing of sales growth when the product has been accepted by most potential buyers; and (4) decline-the decline of sales that results as the product is replaced (by a substitute) or as it goes into disfavor.