These words pertain to the mental capacities or qualities of people. Mind is the most general and most neutral. It may refer exclusively to mental facility; in this case it is usually qualified to indicate how strong or weak such facility is: challenges that stimulate those students with good minds ; a mind too dull to grasp present-day scientific theories. The word can also refer to a bundle of mostly conscious attitudes (including the will), or to the whole psyche, conscious or unconscious, and its powers of comprehension, analysis and inquiry: those who have set their minds against intolerance; a mind afflicted by irrational impulses; a statesman with a great mind . It is also used in philosophy to denote the sum of man’s mental faculties, including those supposedly independent of the physical brain and nervous system: mind over matter. The remaining words are all more nearly restricted to mental ability or rational faculties alone.

Intellect and intelligence both refer more exactly and more formally than mind to mental ability. Intellect is usually applied only to man, and suggests a loftier, more finely developed and more esteemed faculty than the more widely used intelligence , which generally denotes innate capacity to perform mental tasks, to remember, to solve problems and to perceive relationships.

• Dr. Smith is a man of great intelligence but Professor Brown earns the respect of his colleagues for his high intellect .

Intelligence is also the term preferred to suggest lack of mental skills or the degree to which they are possessed singly or in combination: a class of low intelligence ; weak in mechanical skills but reflecting above-average intelligence ; tests to determine verbal intelligence in pre-school children.

Brains , head and wits are all very informal words for aspects of intelligence. Head , the most restricted, usually pertains to a single faculty, often of a practical nature: a good head for figures; keeping a cool head throughout the crisis. Brains suggests a wider scope, like intelligence, but often refers to mental ability that has practical results: It takes brains to land a cushy job. Wits refers specifically to alertness or sensitivity rather than to a general mental facility: warning him to keep his wits about him. Like mind , it can also refer to the conscious or rational intelligence: scared out of her wits. Nous is even more informal than brains for general intelligence and common sense. While conveying some suggestion of cunning it is not a pejorative term and usually combines the notions of practical common sense and intellectual ability: With his nous he is sure to get the job he wants.

Reason refers solely to the objective, rational part of the mind; it is one aspect of intelligence. In use, it is referred to as though it were a technique, rather than a faculty: using reason to trace the murderer from the clues surrounding the crime. The word may also, like one use of wits , refer in a common-sense way to normal sanity: lost his reason . As an abstract noun, it can indicate a rational, unemotional, open-minded approach: the hope that reason rather than prejudice would prevail in the community.