External association

External association is when two things are connected or related to each other, but they are not actually part of each other. It's like how you have a toy car and a toy track. The car is not part of the track, but it can run on it.

In the same way, in science or research, external association means that two things are connected to each other, but they are not actually part of each other. For example, if we wanted to study how eating vegetables affects our health, we might look at data that connects people who eat more vegetables with having healthier bodies. This is an example of external association because the two things are related, but eating vegetables is not actually part of our bodies.

Another example would be a study that looks at how pollution affects the environment. We might see that areas with more pollution have more health problems or less biodiversity. This is external association because pollution is not actually part of the environment, but it can have an impact on it.

So basically, external association is when two things are connected, but they are not actually part of each other. It's like how your toy car and track work together, even though they are separate things.