What is the invasion of body tissues by disease-causing pathogens known as?

The invasion of body tissues by disease-causing pathogens is accurately defined as infection. This process occurs when harmful microorganisms, such as bacteria, viruses, or fungi, enter the body, multiply, and result in tissue damage or dysfunction. The term "infection" specifically refers to this state of invasion and can vary in severity, ranging from asymptomatic cases to serious illnesses.

Infectious disease, while related, refers to the condition that typically manifests as a result of an infection, often characterized by specific symptoms and signs. Contagion refers more specifically to the ability of a disease to spread from one individual to another, while immunity relates to the body's ability to resist or fight off infections. Therefore, while these terms are interconnected, infection is the precise term that describes the initial invasion of pathogens into body tissues.