The saturation point is the point at which an object has absorbed as much of a substance as it can. All objects have such a point for each type of substance they can potentially absorb. Substances absorbed can include liquid, gases, chemicals and energy. Once the saturation point has been reached, no additional amount of the saturating substance can be absorbed.
Perhaps the most common example of the saturation point is a sponge that has absorbed all the water or other liquid it can absorb. When a sponge soaks up water, the water displaces the air held in the pores and chambers of the sponge. Once all the air has been displaced, the sponge can no longer absorb fluid. Additional fluid applied to the sponge will simply leak out.
Another common example involves air. The Earth's air can hold a certain number of molecules under any given condition. When the air becomes saturated, the dew point is reached.
In chemistry and physics, the term can also apply to the absorption of chemicals or energy. Once an object has reached its saturation point, additional energy will have to go elsewhere. The term could alternatively be used to refer to light. Every object and solution is capable of absorbing a certain amount of light, no matter how small that amount may be. Once the maximum amount of light is absorbed, additional light will be refracted or "bounced off" the object.
It is important to note that items have different saturation points. This applies even to very similar items. Size, of course, plays a role in determining how much an object can absorb. A larger sponge, for example, will have a higher saturation point than a smaller sponge. Density is also important — a sponge with more holes will absorb more than one with fewer holes.
Temperature is another key factor in determining the saturation point. Both the temperature of the object or solution absorbing the substance and the temperature of the substance itself will cause variations in the amount of substance that can be absorbed.
While the term was originally coined as a science term, it has come into common use to describe people in certain situations. A person who has learned a large amount of new information in a short period of time might be said to have reached his "saturation point." The phrase might also be applied to someone who has drunk as much alcohol as he can manage.