When you fall behind in your work, you may be said to fail to keep up. It can be helpful to know some synonyms for this phrase to express the same idea with different words. Some alternatives to "fail to keep up" include "fall behind," "lag behind," "trail behind," "straggle," and "retard." Each of these phrases implies the idea of not being able to keep up with the pace of progress. Whether you are having trouble keeping up with a class or a project at work, using one of these synonyms can help you communicate your struggles with clarity and precision.