keep up

verb6

1. •
   To maintain; to preserve; to prevent from deteriorating or falling.

   • The NRA is pumping groundwater into the River Itchen in Hampshire to keep up its flow and is trying to save three streams, the Tong, the Little Stour and the Dour from going dry this summer. — 1992
2. •
   To maintain position; to prevent oneself from falling behind; to stay even or ahead of another while walking, driving, etc.

   • They ran so fast I could hardly keep up.
3. •
   To ensure that one remains well-informed about something.

   • I always try to keep up with (or "keep up on") current affairs.
4. •
   To continue with (work, etc).

   • Keep up the good work, team!
5. •
   To prevent someone from going to bed or to sleep

   • The crying baby kept me up all night
6. •
   (no longer used) To use capital letters as much as reasonable.