In economic and marketing theory, services are defined by four fundamental characteristics: 1. Intangibility (services cannot be touched, seen, or tested before purchase); 2. Inseparability (production and consumption occur simultaneously and cannot be separated from the service provider); 3. Variability or Heterogeneity (service quality can fluctuate significantly depending on who provides it, when, and where); and 4. Perishability (services cannot be stored, warehoused, or inventoried for future sale if unused).