What term describes an organism that causes diseases?

The term that describes an organism that causes diseases is "pathogen." Pathogens are microorganisms such as bacteria, viruses, fungi, and parasites that can invade the body and disrupt its normal functions, leading to illness or disease. Understanding that pathogens are the agents responsible for causing disease is crucial in studying infectious diseases and public health, as it underscores the importance of prevention and treatment measures.

In contrast, vectors are organisms, often insects, that carry and transmit pathogens to other hosts without necessarily causing disease themselves. Antibodies are proteins produced by the immune system to identify and neutralize pathogens, while lymphocytes are a type of white blood cell that plays a critical role in the immune response. Recognizing these different roles helps to distinguish how various biological entities interact within health and disease contexts.