Retention means keeping or holding onto something over time. When you study vocabulary words and can still remember them weeks later, that's retention: your brain has retained the information. When a company talks about customer retention, they mean keeping customers who come back again and again rather than losing them to competitors.

The word appears in many contexts. Schools measure student retention to track how many students stay enrolled from year to year. A sponge has good water retention because it holds liquid without dripping everywhere. Your memory retention can improve when you practice recalling information instead of just reading it once.

Retention is the opposite of loss or forgetting. A bucket with holes has poor water retention. If you cram for a test the night before, you might pass it but have terrible retention: the facts slip away as soon as the test ends. When you truly learn something through practice and understanding, retention comes naturally. Musicians practice scales daily and athletes run drills to build retention of skills that will stick with them.

Notice how retention always involves a time element: you have something now and still have it later when it matters.