The phrase "keep an eye on" is commonly used to describe the act of monitoring or watching closely. However, there are several synonyms that can be used interchangeably to convey the same meaning. These include keeping a watch on, observing, monitoring, scrutinizing, surveying, supervising, checking, inspecting, and guarding. Each of these synonyms can be used to emphasize a slightly different aspect of monitoring, such as the need for close scrutiny, the importance of regular checking, or the necessity of guarding against intruders. Regardless of the specific synonym used, the key idea is to keep careful track of something or someone to ensure their safety, security, or well-being.