There are several synonyms for the phrase "be kept in", some of which include being held, being contained, being confined, being stored, being retained, being reserved, being detained and being locked up. Each synonym has its own context, for instance, being confined could refer to being stuck in one place while being retained usually relates to being held back from advancement or being stopped from progressing further. Being reserved usually applies to keeping resources or supplies for future use while being locked up could be seen as a constrained situation that hinders mobility. Understanding the context of each synonym is critical in using them interchangeably in speech or writing.