To keep up means to move or work fast enough to stay even with others. If you're on a hike and your friends walk quickly, you need to keep up or you'll fall behind. In class, if a teacher explains something rapidly, you might struggle to keep up with the lesson.

The phrase also means maintaining the same level or standard over time. A champion swimmer must keep up her training to stay competitive. A musician needs to keep up his practice to maintain his skills. When your room gets messy during a busy week, you might find it hard to keep up with the cleaning.

People also use this phrase when staying informed. If you read the newspaper regularly, you're keeping up with current events. When you call an old friend to learn what's happening in their life, you're keeping up with them.

Sometimes the phrase suggests effort or difficulty: “I can barely keep up!” means something is moving faster than feels comfortable. Keeping up means maintaining your position or pace, whether that's matching someone's speed in a race, staying current with your responsibilities, or following along as you learn something new.