Brain refers to the control center of the central nervous system of an animal located in the skull which is responsible for perception, cognition, attention, memory, emotion, and action. It commonly describes an intelligent person, by analogy with a human brain, the part of a machine or computer that performs calculations, and oral sex, which gives the term a broader and more practical sense than a single short definition would suggest. Depending on context, it can also point to mind, to dash out the brains of; to kill by smashing the skull, and to strike (someone) on the head, so the category can cover literal uses, related ideas, and more figurative extensions of the same core meaning. Taken together, these meanings present Brain as a flexible theme rather than a narrowly technical label, covering the central idea people usually mean when they use the word while still leaving room for closely related senses that appear in real language. Additional shades of meaning include to destroy; to put an end to and to conceive in the mind; to understand, which reinforce how the category can stretch across adjacent but still recognizable uses of the same term. Brain therefore works well as a quotation category because it can hold direct statements about the subject, figurative uses that borrow its meaning, and broader reflections that stay anchored to the same central idea.
