Retention (noun)

1. The action of keeping or preserving something, especially information, in one's mind or memory.
2. The state of being held back or contained, especially in a particular place.
3. The ability of a material or substance to keep its physical and chemical properties without significant deterioration or loss.

Origin:

From the latin retentio meaning a holding back, from retinere meaning to hold back.

Examples:

1. The teacher was impressed with his retention of knowledge.
2. The retention of water in the soil is important for plants.
3. The company's retention policy aims to keep employees for a longer period.
4. The new memory device promises better data retention.
5. The retention of key employees is a challenge for the company.