any disease of the mind; the psychological state of someone who has emotional or behavioral problems serious enough to require psychiatric intervention
a clear and telling mental image; "he described his mental picture of his assailant"; "he had no clear picture of himself or his world"; "the events left a permanent impression in his mind"
a measure of a person's intelligence as indicated by an intelligence test; the ratio of a person's mental age to their chronological age (multiplied by 100)
an ability to understand the meaning or importance of something (or the knowledge acquired as a result); "how you can do that is beyond my comprehension"; "he was famous for his comprehension of American literature"