Why are density dependent factors based on population size?

Density-dependent factors include disease, competition, and predation. Density-dependant factors can have either a positive or a negative correlation to population size. With a positive relationship, these limiting factors increase with the size of the population and limit growth as population size increases.

Just got this from the internet but I hope it helps

Organism, organ system, organs, tissue, cells

Abay where the river empties into the sea