Systemic acquired resistance (SAR) is a term used in plant pathology to describe the ability of plants to develop resistance against pathogens following an earlier attack. This process involves the production of hormones and other signaling molecules that activate the plant's innate immune system. Synonyms for SAR include induced systemic resistance (ISR), systemic acquired acclimation (SAA), and systemic disease resistance (SDR). ISR is usually used to describe the activation of plant defense mechanisms by beneficial microorganisms, while SAA refers to the ability of plants to adapt to environmental stresses through SAR mechanisms. SDR is a broader term that encompasses both plant-pathogen and plant-pest interactions. However, regardless of the term used, all these processes describe the plant's ability to defend itself against disease-causing agents.