This document discusses different theories and classifications of intelligence. It defines intelligence as the general mental capacity to reason, think abstractly, and adapt to new situations. Intelligence is classified as concrete, social, and abstract. Gardner's theory proposed multiple intelligences including linguistic, logical-mathematical, spatial, bodily-kinesthetic, interpersonal, intrapersonal, naturalist, musical and more. Intelligence quotient (IQ) measures intelligence as a ratio of mental to chronological age. Theories of intelligence include Spearman's two-factor theory of general and specific intelligence, Thurstone's multiple factor theory, and information processing theories. Understanding intelligence helps nurses tailor care and explanations to patients' cognitive abilities.