endogenous

Imagine a plant growing in your garden. Some changes happen because of sun, water, or wind, but others begin inside the plant itself. When something comes from within the system rather than from outside it, it is "endogenous." The word describes things that are produced or shaped from inside, whether the system is a living body, an economy, or a social group.

Think about your body temperature. It is controlled by internal systems, not only by the weather around you. Economists also talk about "endogenous variables"—things that are decided within a model rather than added from the outside. In everyday terms, it means "coming from inside" or "produced within."

"Endogenous" describes processes, substances, or variables that originate from within a system, as opposed to "exogenous," which means originating externally. It's a term frequently used in biology, medicine, economics, and social sciences to emphasize internal origins and self-sustaining mechanisms.

In biology, endogenous hormones are those produced by the body itself (like insulin), contrasting with exogenous hormones administered from outside. In medicine, an endogenous infection develops within the body, while an exogenous one comes from an external source.

Economists use "endogenous" to describe variables determined within their economic models—for example, price and quantity are often considered endogenous because they're influenced by supply and demand within the model itself. Conversely, something like a global oil shock would be considered exogenous, as it originates outside the modeled system.

In social sciences, you might talk about "endogenous preferences," meaning that people's tastes and values aren't fixed but are shaped by their experiences within society.

The word comes from Greek roots: endo- meaning "within" and -genous meaning "born" or "produced." So, endogenous literally means "born within." It's a powerful term for highlighting the importance of internal dynamics and self-regulation in complex systems—reminding us that things aren't always just driven by outside forces.