When it comes to the phrase "on alert," there are several synonyms that can be used to express the same concept. Some examples of these include "vigilant," "watchful," "alerted," "attentive," and "ready." Each of these words serves to emphasise the importance of being aware of one's surroundings and being prepared to take action when necessary. Whether watching for potential danger, waiting for an important call or email, or simply being alert to changes in one's environment, these synonyms for "on alert" can help convey the sense of heightened awareness and readiness that comes with being alert.