Up-to-date means having the most recent and current information, or being modern and not outdated. When your textbook is up-to-date, it includes the latest discoveries and facts. When someone is up-to-date on a TV series, they've watched all the newest episodes and know what's happening now.

The phrase suggests being current in a world that's always changing. A doctor stays up-to-date on medical research so she can give patients the best care. A phone's software needs to be kept up-to-date with the latest version so it works properly and stays secure. An up-to-date map shows new roads and buildings, not just what existed years ago.

You might use this phrase when catching someone up on your life: “Let me bring you up-to-date on what's been happening since summer.” Or a teacher might ask if your immunizations are up-to-date before a field trip. The opposite would be outdated or behind the times. Being up-to-date means you have the current story, the fresh facts, or the latest version of something that matters.