Saline means containing salt or relating to salt, especially salt dissolved in water. When doctors talk about a saline solution, they mean water with salt mixed into it, similar to ocean water but much less salty and carefully measured for medical use.

You've probably encountered saline if you've ever had an IV at the hospital. That clear liquid dripping through the tube is saline solution, which helps keep patients hydrated. Nurses also use saline to clean wounds or rinse out eyes because it's gentle and won't irritate sensitive tissues. Contact lens wearers store their lenses in saline solution overnight to keep them clean and moist.

Ocean water is saline because it contains dissolved salt. Some lakes, like the Great Salt Lake in Utah, are so saline that swimmers float more easily than in regular water. When scientists describe soil as saline, they mean it contains too much salt for most plants to grow well. The concentration of salt matters tremendously: a little bit of saline can be helpful or harmless, while too much can damage living things.