Clouding of consciousness, also called brain fog or mental fog, occurs when a person is conscious but slightly less wakeful or aware than normal. The term "brain fog" is used to represent a subjective condition of perceived cognitive impairment. A 2023 review article defined brain fog as "a phenomenon of fluctuating states of perceived cognitive dysfunction that could have implications in the functional application of cognitive skills in people's participation in daily activities". Sufferers may be less aware of time and their surroundings, and find it difficult to pay attention. People describe this subjective sensation as their mind being "foggy".