delusion noun

ADJ. dangerous | foolish I thought the whole idea was just a foolish and dangerous delusion. | paranoid

VERB + DELUSION get, have, suffer (from) The psychiatrist said she was suffering from paranoid delusions.

PREP. under a/the ~ He seemed to be under the delusion that he would make his fortune within a few years. | ~ about He had no delusions about his feelings for Kate. | ~ of She had delusions of persecution.

PHRASES delusions of grandeur (= a belief that you are more important than you actually are) Don't go getting delusions of grandeur.