Specific language impairment (SLI) is diagnosed when a child's language does not develop normally and the difficulties cannot be accounted for by generally slow development, physical abnormality of the speech apparatus, autism spectrum disorder, acquired brain damage or hearing loss.
Perfect competition. A perfectly competitive market is a hypothetical market where competition is at its greatest possible level. Neo-classical economists argued that perfect competition would produce the best possible outcomes for consumers, and society.
niche marketing. Concentrating all marketing efforts on a small but specific and well defined segment of the population. Niches do not 'exist' but are 'created' by identifying needs, wants, and requirements that are being addressed poorly or not at all by other firms, and developing and delivering goods or services to satisfy them.