brain
When used to describe the physical organ, 'brain' is a countable noun. For example, you can talk about 'the human brain'. When referring to intelligence or mental ability in general, it is often used in singular form (e.g., 'a brain for business'). In casual conversation, calling someone 'the brain' of a group means they are the smartest person or the one who makes all the plans. As a verb, you will almost always see 'brain' as part of the compound word 'brainwash'. It is rarely used on its own to mean indoctrination.
💬Casual Conversation
my brain is actually fried from this cramming session.
DRINK SOME WATER DEAR. LOVE GRANDMA
Meanings
The organ of soft nervous tissue contained in the skull of vertebrates, functioning as the coordinating center of mental activity.
"The human brain is incredibly complex."
The intellectual capacity or intelligence of a person.
"She has a brilliant brain for mathematics."
A person who is exceptionally intelligent or the primary planner of a project.
"He was the brain behind the entire operation."