memory

Memory is the faculty of the mind to encode, store, and retrieve information acquired from experience. In humans, it encompasses a range of processes and lasts across time, from fleeting sensory impressions to long‑lasting knowledge. Broadly, memory is divided into sensory memory, short-term or working memory, and long-term memory.

Sensory memory holds brief impressions of sensory input; short-term or working memory keeps limited information actively in use, typically for seconds to minutes and in the range of several items. Working memory also involves manipulation of held information to guide thought and action. Long-term memory stores information over longer periods and comprises explicit or declarative memory (episodic memory for events, semantic memory for facts) and implicit or nondeclarative memory (procedural skills, priming, and conditioned responses).

The hippocampus and surrounding medial temporal structures are central to forming new explicit memories, while cortical areas store the semantic and perceptual aspects. Subcortical structures, such as the amygdala and cerebellum, contribute to emotional and procedural memories. Memory involves encoding, consolidation, and retrieval. Encoding can be enhanced by attention, elaboration, repetition, and spacing. Consolidation stabilizes memories, a process that continues after learning and is reinforced during sleep. Reconsolidation can modify memories upon retrieval.

Memory in computing refers to data storage capacity and organization. Primary memory (RAM) is fast and volatile, whereas secondary storage (hard drives, SSDs) retains data without power. The memory hierarchy also includes caches and registers, balancing access speed and capacity.

Memory is not a perfect record; forgetting, interference, retrieval failures, and misinformation can alter memories. Understanding memory integrates insights from psychology, neuroscience, and computer science to explain how experiences are encoded, stored, and later retrieved.