Concentration (noun)

1. The act or state of focusing one's attention or mental effort on something.
2. The degree to which a particular substance is dissolved in a particular solvent.
3. The amount of a particular substance present in a particular quantity of another substance or mixture.

Origin:

Late middle english: from latin concentratio(n-), from concentrare "bring together".

Examples:

1. He was able to maintain a high level of concentration throughout the exam.
2. The concentration of salt in the water is too high.
3. The company checks the concentration of sugar in their product.
4. The concentration of pollution in the air is getting worse.
5. A high concentration of people live in this area.