Retain means to keep or hold onto something rather than losing it or letting it go. When you retain information from a lesson, you remember it days or weeks later instead of forgetting it right after class. When a sponge retains water, it holds the water inside its pores even after you lift it from the sink.

The word often appears when keeping something requires effort or intention. A baseball team might retain its championship title by winning again the next season. A company retains its best employees by treating them well and paying them fairly. Your body retains heat on a cold day by trapping warmth, like when you put on a coat.

In legal contexts, people retain lawyers, meaning they hire them and keep them available for advice. The word suggests an ongoing relationship or continuous holding rather than a one-time event.

The opposite of retain is to lose, release, or let go. If you can't retain what you study, the information slips away. Strong retention means holding onto things effectively, whether that's remembering facts, keeping customers coming back to a business, or a dam retaining water behind its walls. When something has good retention, it keeps what it's supposed to keep.