What is characterized by excessive feelings of tiredness during the day?

Daytime sleepiness is characterized by excessive feelings of tiredness or drowsiness during the waking hours. This condition can manifest as an overwhelming urge to sleep during the day, which significantly impacts one's ability to stay alert and function effectively. It can be caused by various factors including inadequate sleep at night, sleep disorders such as sleep apnea, or lifestyle factors.

In contrast, chronic fatigue syndrome involves a more complex set of symptoms beyond just daytime tiredness and includes persistent fatigue not improved by rest and often associated with other symptoms like joint pain or cognitive difficulties. Sleep deprivation, while it can lead to daytime sleepiness, specifically refers to not getting enough sleep, which typically relates to a specific period of inadequate rest rather than a chronic state. Hypersomnia, although it implies excessive sleepiness, includes conditions where individuals may sleep excessively at night, yet still feel tired during the day. Understanding the nuances helps clarify that daytime sleepiness is specifically focused on the experience of feeling sleepy during waking hours, making it the most appropriate answer in this context.