Wakeful is an adjective that describes the state of being alert, or unable to sleep. There are several synonyms for this term, which can be used in different contexts to convey similar meanings. For instance, the term vigilant is often used to describe a state of watchfulness or attentiveness. The word alert also has a similar meaning, referring to a state of readiness or awareness. Meanwhile, observant suggests being attentive or keeping a close eye on things. Additionally, watchful, attentive, and vigilant can also be used to convey wakefulness, as they all indicate a state of being awake and alert. Finally, the term insomniac is sometimes used as a synonym for wakeful, describing a person who suffers from insomnia and has difficulty sleeping.