The difference between Crazy and Mentally ill

When used as adjectives, crazy means insane, whereas mentally ill means having a psychological disorder.

Crazy is also noun with the meaning: an insane or eccentric person.

Crazy is also adverb with the meaning: very, extremely.

check bellow for the other definitions of Crazy and Mentally ill

Crazy as an adjective:

Insane; lunatic; demented.

Examples:

"His ideas were both frightening and crazy."
Crazy as an adjective:

Out of control.

Examples:

"When she gets on the motorcycle she goes crazy."
Crazy as an adjective:

Overly excited or enthusiastic.

Examples:

"He went crazy when he won."
Crazy as an adjective:

In love; experiencing romantic feelings.

Examples:

"Why is she so crazy about him?"
Crazy as an adjective (informal):

Very unexpected; wildly surprising.

Examples:

"The game had a crazy ending."
Crazy as an adjective:

Characterized by weakness or feebleness; decrepit; broken; falling to decay; shaky; unsafe.

Crazy as an adverb (slang):

Very, extremely.

Examples:

"That trick was crazy good."